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E28 (1982 - 1988)

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  #1  
Old 08-13-2011, 02:10 PM
Ataglance Ataglance is offline
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No Power to Transfer pump

The wires, one green/yellow and the other brown, are dead. Where do they hook up to for electrical supply, like a fuse or relay or something?

All help is greatly appreciated.
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  #2  
Old 08-13-2011, 05:21 PM
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I would think it would come out of the fuse box or the relays next to the box. The number 1 fuse and the number 2 relay are for the fuel pumps. The Bentley manual has alot of electrical circuit diagrams. You may want to consult one.
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  #3  
Old 08-13-2011, 06:45 PM
Ataglance Ataglance is offline
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kill switch?

Still trying to operate my transfer pump. Does 528e have a kill switch or something like that and where is it?

Fuse and relay seem okay but I cannot figure out if the transfer pump goes to relay 2. Thanks.
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  #4  
Old 08-14-2011, 06:06 AM
Tecmec Tecmec is offline
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Both of your fuel pumps are fed from the fuel pump relay then through fuse number 1. The green and yellow wire is hot. The brown is gound. There are three connectors in the line to both pumps. C101 (17 pin) (Pumps are fed by pin 7) located in the engine compartment on the right side of the fuse block. C206 (29 pin) (Pumps are fed by pin 27)located under left hand side of dash. C250 (13 pin) (Pumps are fed by pin 7) located under center of the rear seat. Ground G301 is located under the rear seat on the left hand side. The pins on C101, 206, and 250 are pretty well isolated from foul weather, ETC. While the ground is as well, I would disconnect G301 and make sure I have a good clean connection. Also, pull C250 and see if you have power at pin 7. You should pull the pump and read it out. I believe an earlier posting of yours identified that you had a connector problem at the auxiliary pump. Make sure neither of the pins in the connector on the pump flange are bad. Many times they corrode off and come out when you remove the connector on the pump flange.
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  #5  
Old 08-14-2011, 03:29 PM
Ataglance Ataglance is offline
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Well the connections seem to be okay best I can tell. A jumper wire starts the pumps w/o the relay. The relay was changed. The pumps were tested with a battery and they work.

If the pumps still don't run when the ignition is turned on, what does that mean? Is there some type of kill switch?

The help is greatly appreciated
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  #6  
Old 08-14-2011, 07:27 PM
Tecmec Tecmec is offline
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There is no "Kill Switch". The fuel pump relay gets activated by a signal from the motronic control unit (MCU, on board computer) through the main relay. When the ignition switch is turned to run, power closes the main relay sending power from pin 87 of the main relay to pins 18 and 35 of the motornics unit (not sure of your exact model, could be pin 16 instead of 18 but try 18 first). From here power leaves through pin 20 of the motronics unit to the fuel pump relay at pin 85. This activates the fuel pump relay and power goes from the battery into pin 30 of the fuel pump relay and out pin 87 on to connector C101 (cited earlier) and on to the pumps. You should disconnect the MCU connector (disconnect the battery when ever you disconnect or connect this connector). Once disconnected, with the ignition at run you should beable to hear the pumps run when pin 20 is jumpered to ground. If you do not hear the pumps you should check pins 16 and 35 for battery voltage. If you do not have power to one or both of these pins you need to check for a problem with one or both of the red/blue wires going from pin 87 of the main relay to the MCU. Pins 16 and 35 are the power supplies to the MCU. If you have no power going to the MCU in either of these pins, the vehicle will not run. If pin 20 to ground runs the pumps and you have battery voltage at pins 16 and 35 the problem could be in the MCU itself. Note; I am assuming you have the small diagnostic connector and that your MCU connector is the two row 35 pin connector (top left is 1, top right is 18, bottom left is 19 and bottom right is 35) and not the three row 55 pin connector. If I am wrong get back to me and we will go from there.
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  #7  
Old 08-14-2011, 07:30 PM
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Quote:
Originally Posted by Ataglance View Post
Well the connections seem to be okay best I can tell. A jumper wire starts the pumps w/o the relay. The relay was changed. The pumps were tested with a battery and they work.

If the pumps still don't run when the ignition is turned on, what does that mean? Is there some type of kill switch?

The help is greatly appreciated
I'm not aware of any kill switch but some recent posts suggest that maybe your ignition switch could be bad. Or maybe the main relay.
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  #8  
Old 08-14-2011, 08:24 PM
Tecmec Tecmec is offline
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Looking at your garage listing I probably led you wrong in my earlier posting about the Motronics Control Unit (MCU). I now assume you have the larger diagnostic connector and the 55 pin MCU connector. The wiring path I gave you is still good but the testing of the MCU is different. You should have battery voltage between pin 18 and ground with the ignition off, battery voltage between pin 27 and ground with the ignition on, and battery voltage between pin 37 and ground. You should use a fused jumper wire for the pin 37 check. The fuel pump is run off of pin 3. If you go between pin three and ground with a fused jumper wire you should hear the pumps run. Sorry for the misinformation.
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  #9  
Old 08-15-2011, 11:01 AM
Ataglance Ataglance is offline
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The gas gauge correctly reads just under half full but the light next to E stays on.

Does that mean anything? Thanks.
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  #10  
Old 08-15-2011, 12:29 PM
Ataglance Ataglance is offline
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Hi,

I have a two row, I 20 pin operation motronic, if that helps.
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  #11  
Old 08-15-2011, 12:32 PM
Tecmec Tecmec is offline
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That light is driven strickly from a switch located in the fuel tank sender which closes at about 1.5 gallons. The problem could be a bad or stuck switch or a VDO problem. You might be advised to pull the sending unit so you can measure the actual level in the tank with a wooden dowl or similiar item to see if the gauge is following the actual level. I.E. do you really have 1/2 tank when it reads 1/2 tank. Caution, insure you disconnect the battery negative cable to avoid any sparks opening or when the tank is open. Also, remove the gas filler cap to insure no pressure is in the tank. Remember you need to remove the sending unit from the flange before your remove the pump flange nuts. Other wise you will not be able to position the pump at the correct angle to remove it from the tank. Many of these older vehicle have VDO problems. Also some of the VDO have two AA batteries on the board that when gone can impact or affect the VDO operation. I do not know if or how they relate to the fuel gauge. I believe the fuel gauge and light are pretty much stand alones and do not relie to heavly on the VDO circuit board. Do you have an onboard computer? The fuel gauge feeds that input. If so, what does it tell you regarding amount of gas left. Regarding the sending unit. You can test the sending unit if you remove it. It has a three wire plug on top. Looking into plug, Left if 31 center is G, and right is W. Moving the float slowly from empty to full (bottom to top) and reading continuty between pins G and 31 you should see resistance continuously changing (no breaks in continuity). At empty you should have about 71 ohms give or take a few. At full you should have about 3 ohms. At empty you should should have continuity between pins W and 31. Remember you are dealing with a volitile fuel hear. Caution, awareness, and safety must be the watch word. If not comfortable in this environment seek help. Safety first. I never work on fuel systems inside a structure. I never work on fuel systems with out an assistant and safety equipment near by. it only takes one mistake.

Last edited by Tecmec; 08-15-2011 at 12:36 PM. Reason: Replace blocked word
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  #12  
Old 08-15-2011, 12:48 PM
Tecmec Tecmec is offline
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Engine Control Unit ECU

Sorry, I am confused. I expected you had a 35 pin Motronics connector which represents the basic Motronics system and was used on the 528 up through March 1987 or the 55 pin Motronics connector which was used on the post March 87 and 88 528s. The 55 pin was the advanced Motronics 1.1 system. Could we be talking about two totally different connectors? I am referring to the motronics unit I believe to be located under the right side dash above or behind the glove box. The interior lower dash panel on the right side and the glove box must be removed for access. The Basic Motronics system had a 15 pin diagnostic connector mounted under the hood. The Motronics 1.1 has a larger 20 pin diagnostic connector mounted under the hood. Both are mounted in the area of the intake manifold.
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  #13  
Old 08-16-2011, 07:54 PM
Ataglance Ataglance is offline
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You're right. It does have three rows I was looking at the diagnostic hookup under the hood.

There is voltage at 27 and 36. But connecting the ground to 3 does not run the pumps. Ran these test a couple times.

Thanks in advance.
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  #14  
Old 08-16-2011, 09:56 PM
Tecmec Tecmec is offline
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OK. Let me restate some of this. You should have battery voltage with ignition off between pin 18 and ground. You should have battery voltage with ignition on between pin 27 and ground. You should have battery voltage, between pin 37 and ground when, at the same time, you put a fused jumper between 36 and ground. LIkewise, you should hear the pumps run between pin 3 to ground when, at the same time, you put a fused jumper between 36 and ground. When you put the fused jumper between pin 36 and ground you should hear the main relay click. To make a good test of the main fuel pump you can either remove the pump and hot wire it with battery voltage. Positive to one terminal and Negative to the other terminal. If the pump is good you will hear it spin. Or you can run two long lengths of 14 or 16 gauge wire from the battery to the pump terminals while it is still installed. Either case you should hear the pump run. You can also test the pump by removing the fuel pump relay and running a jumper between pin 30 and pin 87 of the relay block. It is recommended that this jumper be a fused jumper with a toggle switch in line. You would plug it into the two pins and throw the toggle to activate the pump. If you do this and the pump does not run check to see if you have battery voltage between pin 30 and ground. Also, it is easy to swap or move the main relay and fuel pump relay positions. So make sure you have the right relay. The main relay should have red/white wires coming out of the one pin 87 and red/blue out of the other pin 87. The fuel pump relay has only one pin 87 and a green/violet wire should be coming out of it. Pin 85 of the fuel pump relay has a brown/green wire coming out of it. The basic power path for both the main and transfer pump is from positive battery to pin 30 of main relay and pin 30 of fuel pump relay, from main relay pin 87 to fuel pump relay pin 86. Motronics activates the main relay which activates the fuel pump relay. Power from fuel pump relay pin 87 goes through fuse #16 to the one side of the pump motor. The other side of the pump motors goes to ground (G301). If you jumper fuel pump relay block pins 30 and 87 and fuse 16 is good the pumps should run if ground G301 is good. Again, remember Safety. Also, it does not hurt to disconnect the battery negative cable when you are removing or installing the relays or disconnecting or connecting the ECU connector, or most any connector for that matter. It prevents unwanted sparks and or power spikes or shorts that can damage sensative electronics.
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  #15  
Old 08-17-2011, 02:47 PM
Ataglance Ataglance is offline
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Hi Tecmec,

Great Help, thank you. I did the tests and this is what I got:

1. No voltage b/n 18 & ground with the ignition off but I think 18 is empty. No voltage at 19 or 17 either.
2. voltage b/n 27 & ground w/ the ignition on.
3. voltage b/n 37 & ground when 36 & ground are connected.
4. I heard a click when 36 & ground were connected.
5. Did not hear pumps when 36 & ground and 3 & ground were connected.

I hooked the pumps up to the battery and they run. I also hotwired them at the relay and they ran.

I did not use a fused jumper wire, just a regular wire.

You think the ECU is bad or am I badly connected?
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  #16  
Old 08-17-2011, 07:55 PM
Tecmec Tecmec is offline
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I would not be ready to point the finger at the ECU yet. You most likely are, but lets make sure we are reading out the ECU connector correctly. Looking at the connector, the top row is the one with 19 pins, the middle and bottom both have 18 pins. Looking at the connector the pin numbering sequence goes from right to left. Pins 1, 20, and 38 are on the right and pins 19, 37, and 55 are on the left.The power comes from the battery and feeds the main relay and the fuel pump relay. both have to be activated to run the pumps. A couple more checks. Do thes following checks with the relays installed. You can pull the relay and their sockets up and out of there mounts to do the check. Read voltage between pump relay pin 87 and ground when pin 3 of the ECU connector is grounded and 36 is grounded. You should have battery voltage. Pin 36 to ground should activate (the click you heard) the main relay. With the main relay activated, pin 3 to ground should activate the pump relay and run the pumps. With the main relay and the pump relay activated you should have battery voltage at pin 87 of the pump relay. If not the pump relay could be bad. If you have voltage at pump relay pin 87 but no fuel pump run the problem could be the fuse, fuse holder, ETC or wiring between the pump relay and the pumps. With the main relay and the pump relay activated you can read between pin 7 and ground of connector C250 (center under rear seat) (do not disconnect connector, just read the back side of the connector). You would have battery voltage if the wiring from pump relay pin 87, through fuse 16, is good. Checking at C250 pin 7 would check main relay, pump relay, fuse 16, and wiring up until connector C250. If you suspect the pump relay, I believe the horn relay is the same or close enough to use to test the system with a different relay. I. E. pull the pump relay and replace it with the horn relay. You could save some steps by putting the horn relay in place of the fuel pump relay and checking the pin 3 to ground with pin 36 grounded and see if the pumps run. If so the pump relay is bad. If not, we are coming closer to pointing a finger at the ECU.
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  #17  
Old 08-18-2011, 05:10 AM
Ataglance Ataglance is offline
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1. 18 &G, no ignition, 12 volts.
2. 27 & G, ignition on, 10 volts (multimeter set at 50V)
3. 37 & G, 36 & G there is a click
4. 36 & G, 3 & G, no pumps running
5. Relay pin 87 (both main &FP relay) while 36 & 3 are grounded, no voltage. (There is voltage at both pins on both relays) Relays are taken out of connector.

I have the sequence correct now, sorry about that.
Still note getting power when 36 and 3 are grounded.
Purchased new FP relay from dealer, still no power to pumps
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  #18  
Old 08-19-2011, 06:29 AM
Tecmec Tecmec is offline
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OK. We need to recap here a bit. It is unclear to me if we eliminated any issue with fuse #1. I might have incorrectly referred to it as fuse #16 earlier. But fuse #1 is after the main and fuel pump relay but before the pumps. You need to insure fuse #1 or it's blades are OK. Also, you need to insure G301 is clean and tight. In paragraph 3 of your latest post you state you heard the click. Did you also have battery voltage between ECU connector pin 37 and ground. Recheck if not sure. In paragraph 5 it is unclear to me if the relays were installed or removed when you made this test. With relays installed and ignition on you should have voltage at pin 87 of both the main and fuel pump relay when 36 and 3 are simutaniously both put to ground. Likewise you should have voltage at pin 7 of connector C250 and at pin 13 of connector C250. If you have voltage at C250 pin 7 and 13 that eliminates a problem with fuse #1. If you question if the main relay is good you can easily check it by pulling the connector on the idle air stabilizer valve and with ignition on check for voltage between the red/white wire and ground. If voltage is present the main relay is most likely working. Regarding "still no power when 36 and 3 are grounded". The only thing between the battery and ECU connector 36 is the main relay. Pin 86 of the relay is fead by the battery, and pin 85 is the other side of the relay coil. If you have battery voltage at pin 86 (with the relay installed) but not at pin 85 or ECU connector pin 36 the relay is bad and the vehicle will not start and the pumps will not run. If you have power at pin 85 but not ECU connector pin 36 there is a wiring problem. The only thing between the battery and ECU connector 3 is the main relay and the fuel pump relay. Pin 86 of the fuel pump relay is fead by pin 87 of the main relay, and pin 85 is the other side of the fuel pump relay coil. If you have battery voltage at pin 87 of the main relay and pin 86 of the fuel pump relay (with the relays installed) but not at pin 85 of the fuel pump relay or ECU connector pin 3 the relay is bad and the vehicle will not start and the pumps will not run. If you have power at fuel pump relay 85 but not ECU connector pin 3 there is a wiring problem. If all this stuff check out I think you are coming close to putting the finger on the ECU. I am just not sure why. We have been trying to power the pumps without the ECU in the circuit and have not been successful so I am not sure what points to the ECU. I will say I have seen this before and a new ECU ended the issue. Diregarding the pumps for a minute. Are you sure, without a doubt, that you have a good ignition. I.E. have you pulled a plug wire and put a spare plug in the wire, grounded it and saw spark when you turned over the engine. If not you need to confirm this. Also, Did you jumper fuel pump relay pump pin 30 and pin 87. Did the pumps run. If so the issue has to be one of the two relays, a wire integrity issue, or the ECU. Finally, I would make sure all connections and connector contacts are tight and not corroded. There isn't much left unless we are missing the obvious, which can happen. Sorry if I am just helping you spin your wheels.
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  #19  
Old 08-22-2011, 06:46 AM
Ataglance Ataglance is offline
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Hi Tecmec,

I ran these tests a couple of times over the weekend. I must admit I am lost:

BMW Test (Tecmec 8/20/11)

1. Fuse #1 good, replaced 2nd time to be sure
a. Blades? good
2. G301? Not sure how to test.
3. Battery Voltage at 37 &G? , with relay on? NO Off? NO
4. Voltage at Pin 87 at main relay with relay installed & G while ignition on and 36 and 3 are grounded simultaneously? YES
5. Fuel pumps running while 36, 3 are grounded? YES
6. Voltage at Pin 86 of main relay with relay installed and ignition on? NO
a. At pin 85 w/ relay installed and ignition on? NO
b. At pin 36 on ECU connector w/ relay installed and ignition on YES
7. Voltage at Pin 7 of Connector C250 (pin on ECU?) NO
8. Voltage at Pin 13 of Connector C250 (pin on ECU?)? YES
9. Check of Main Relay.
a. Disconnect connect idle air stabilizer valve
b. Turn Ignition on.
c. Voltage b/n red/white wire and ground (from main relay?) Voltage at pin 87.
d. Reconnect idle air stabilizer valve.
10. Voltage at Pin 87 of main relay? There are two pin 87’s. No voltage at middle pin 87 which has a red/white wire coming out, but voltage at other pin 87 with two red/white wires coming out of it.
11. Voltage at Pin 86 of Fuel Pump Relay? YES
12. Voltage at Pin 85 of Fuel Pump Relay? YES
13. Jumper b/n 87 & 30 of Fuel Pump Relay? YES


Other Issues:
1. Is there a 15a fuse b/n pump relay and pumps?
2. Does it matter that there is no continuity on both sides of fuse holder #1?
3. New main relay from O’Reilley’s. They are certain it is correct.
4. New fuel pump relay from the dealer.
5. Voltage at green/violet wire from fuel pump when engine is cranking.
6. Pumps are running when 36 v& 3 are grounded.
7. Voltage at brown/green wire b/n fuel pump relay and ECU.
8. No continuity between both sides of fuel pump fuse when tested with ohm meter with ignition off.

Still only cranking and not starting.

Any thoughts again are greatly appreciated.
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  #20  
Old 08-22-2011, 08:13 AM
Ataglance Ataglance is offline
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transfer pump/gear seelctor switch

Any chance a bad gear selector switch could be my no start/ no power to pumps problem? I think the switch (or sensor) is on the differential?

Engine cranks but does not start. Does ECU need a signal from that to run?

Diff mount came off recently and a new mount was required but the car has not run since.
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  #21  
Old 08-22-2011, 01:01 PM
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Quote:
Originally Posted by Ataglance View Post
Any chance a bad gear selector switch could be my no start/ no power to pumps problem? I think the switch (or sensor) is on the differential?

Engine cranks but does not start. Does ECU need a signal from that to run?

Diff mount came off recently and a new mount was required but the car has not run since.
If you're referring to the nuetral safety switch, its connected to the trans and is not the problem if you car cranks. Did you try starting it by spraying some ether (starting fluid) into the intake? The problem could be in the fuel lines, maybe one got crushed or plugged.
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  #22  
Old 08-22-2011, 05:27 PM
Ataglance Ataglance is offline
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Starting fluid didn't help unfortunately. Fuel system runs fine when pumps are jumped. They just do not want to turn on when the key is turned. New relays too and voltage in the right places as far as I can tell.
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  #23  
Old 08-22-2011, 07:01 PM
south26 south26 is offline
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It could be your reference sensors on your tranny, if they are bad you will not get gas.


Andy
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  #24  
Old 08-22-2011, 07:24 PM
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It could be your reference sensors on your tranny, if they are bad you will not get gas.


Andy
I'm pretty sure the '88 has only the single reference sensor on the front of the crankshaft (motronic 1.1 version).
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  #25  
Old 08-24-2011, 09:38 PM
Tecmec Tecmec is offline
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Confused by your reference to ECU pin when referring to C250. Both C250 and G301 are located under the rear seat. C250 in the center and G301 on the left side. To check G301 disconnect it from the body and check continuity between C250 pin 13 and the lug at G301. After doing so, wire brush body hole for G301 and emory cloth the lug. Reinstall G301. The check at ECU pin 37 to ground is checking voltage supply to ECU. It should be made with pin 36 grounded. With pin 26 gounded, voltage between 37 and ground should be battery voltage. The main relay should be installed and the ignition off. Pin 86 of main relay should always be hot. Likewise pin 85 of main relay should always be hot when 86 is hot. The pin 7 and pin 13 reference is to C250, not the ECU. Pin 7 is before the pumps and pin 13 is after the pumps. It would be impossible to have power, as stated, at pin 13 but not at pin7. On the main relay pin 87 feeds pin 86 of the fuel pump relay. The other pin you refer to is pin 87A. This pin should have a red/white wire coming from it going to the fuel injectors. Fuse #1 is a 16 amp fuse between the fuel pump relay and the pumps. there would only be continuity on both sides of the fuse holder if you had a good fuse installed. it would be the same as touching your probes together. The green/violet wire is on the input side of the pumps. Do you have voltage between the brown wire coming out of the pump and ground when you crank the engine. You can check this by checking for voltage between C250 pin 13 and ground. Do not disconnect C250 when you make this check. Check from the back side of the connector. Don't understand why you do not have continuity across the fuse. With the eception of veifying a couple of the above items, I think it is time to move away from the fuel system and confirm that the ignition system is functioning. If I understand most of your post I believe fuel is not your current problem. I am starting to lean towards a fault in the ignition system, if that all check out fine than I would consider a ECU replacement. You might find one in a vehicle someone is parting out. If you look on the ECU the P/N is prominantly marked. When checking the ignition system becareful of stray voltages and becareful not to ground something. Doing so you can damage some of the electronics. A quick check of spark is to pull a plug wire and plug. Put the plug into the wire and ground the plug to the block when you turn over the vehicle. Hopefully you should see a nice blue spark or at least a white spark. No spark would be a solid indication that we have problems with the ignition system. A Bentley manual would be good for messing with the ignition system because there are alot of precautions you need to follow to protect yourself and the vehicle electronics. The end problem of weak or no spark can be a bad ECU. Before making that call you need to insure the ignition system, the pulse sensor, plugs, wires, distributor cap and rotor are good. If you have spark in the test above I would say they are. if no spark I would check these item, the last being replacing the ECU. Regardless, instead of chasing ghosts in the fuel system let's confirm that the ignition system is good and you have spark. Good luck.
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