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Discussion Starter · #1 ·
Hi folks,

Some back story, first: I have a 1988 325iX Touring (european car). Since I bought it, I've been having intermittent starting problems. 8 times out of 10, it will start when it's cold, but once it's warmed up it will almost always refuse to start. When it will not start, I've tested for fuel by turning the key to "RUN" position, and I'm not seeing any fuel get to the fuel lines (pulled them off the rail and FPR)... so I'm in the process of getting another fuel pump to test with.

I've replaced the Fuel Pump Relay already, as well as the Crank Position Sensor. The car also needed new wires and plugs, so they've been replaced as well (new distributor several months ago). Since it seems to be damp days when it won't cold-start, I'm thinking the coil may be a separate issue, but it could be causing the no-start condition when cold (and damp). I purchased a new temperature sensor (the blue one) that sends to the ECU. I haven't replaced the old one yet though, as I haven't had an opportunity to test.

At the moment, what I've narrowed the issue down to is either the fuel pump itself, or check valve in the fuel pump (which replacing the pump will fix, in both cases). The problem with this is that most people who have the check valve issue report that it takes extra cranking time, but still starts. In my instance, this is not the case at all. When the car decides it WON'T start it won't start...not until it cools down...then it fires right up. This makes me suspect the temperature sensor, because if it thinks the engine is cold it will likely flood it. So...fuel pump/possible temp sensor issue, is causing warm no-start... I believe.

Separately, is the occasional no-start when cold. Again, it seems this is an issue with moisture, which is likely the coil (since the rest of the ignition system has been replaced). It is possible, of course, that it is some other wiring issue that is affected by the moisture, but I'd likely start with the coil.

My question is... is there anything that anyone can think of that would cause these two issues, or am I right to assume that they are two separate issues that are unfortunately working together to confuse the problem? Any input would be helpful. This is my first post. I just want to get these sporadic starting issues resolved so I can move on to other TLC-related fixes for the car.

Thanks!
 

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I do not know the 325iX Touring but presume it is the same as other 325is.

The Fuel Pump Relay does not energize and run the fuel pump when ignition is ON.....I presume this is what you are calling "run" position....only on the "Start" position and then "run".

The ECU picks up the Crankshaft pulses when the engine turns over and then supplies ground to the lower side of the Fuel Pump Relay, pin 85. Pin 86 will already have +12 volts on it from the main relay.

So do not expect to see fuel pumping out of or a noise coming from the fuel pump until the engine starts turning over.

You need to put a voltmeter across pin 86 of the relay with ignition ON...should show +12 volts with respect to ground.

Then put your Black meter lead on pin 85 and the Red lead on the Battery positive and you should see pin 85 go down to ground once the engine starts turning over...the fuel should flow if the pump is getting power and is not broken.

Replace the Blue Sensor and also check that your Throttle Position Switch (TPS) under the throttle body is working properly...should "click" when throttle is relaxed and do not touch the throttle when starting!
 

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Discussion Starter · #3 ·
Thanks Billwill,

You're correct that I was just setting the key to the "RUN" position (not cranking the engine). I was starting to suspect that it doesn't send fuel until it's cranking, but I'd read that it should fire the pump (at least when cold) for a few seconds. This is likely not the case, so I'll be sure to check it when cranking.

Appreciate the help. I'll give your suggestions a try.
 

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Bavarian Autosport
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I would also check the round connector under the intake. The throttle body heater gaskets on these are notorious leakers and the leak gets coolant into this plug and quite often corrodes it badly causing all sorts of running/starting issues.
 

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Discussion Starter · #5 ·
Hi [email protected],

Are you referring to the TPS connector? If so mine is a rectangular 3-pole connector. I will certainly check it. There's also a round connector (non-electrical) that I believe is a vacuum line. Just wanted to make sure I'm looking at the right thing.

Thanks!
 

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Bavarian Autosport
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No i'm referring to the 7 pin twist-lock connector under the intake. Not on the throttle body itself. It sits in a metal bracket bolted to the underside of the intake and it allows the intake to come off without having to unplug all the injectors and the temp sensors. The connector looks like the one on the firewall near the brake booster. Early cars didn't have them I believe they started using it in 9/87 on US models. Not sure on your 88 touring though. If you have this connector check it. If you don't obviously you can't.
 

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livin large
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when the motor is warmed and doesnt start, how long has the car sat after running before starting again? this could be a vapor lock situation.
 

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Bavarian Autosport
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I have an occasional not hot but warm start problem with mine. It always starts but sometimes I have to crank it a lot longer than usual. I've replaced a lot of stuff and come to the conclusion that i've just messed with too much stuff (air flow meter and throttle plate) to get the car to idle reasonably well with a 272 cam and this is a side-effect. I know it will always start but it happened to my wife one day and I don't think she'll ever borrow the car again.

I would change the coil if you get a complete no-start when hot. I had a coil go bad on another car of mine once that was so random it stumped me for about 6 months. Until then I had always been of the mindset that they either worked or they didn't. I was wrong.
 

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Discussion Starter · #9 ·
Did a bit of testing last night, and I definitely have no fuel when in a no-start situation. I pulled the fuel line off the rail and the FPR and put them in a small dish. I then cranked the engine, and no fuel came out at all. I tested for spark, and there was spark... doesn't mean the coil isn't still a problem, but at least I know that it's likely not the crank position sensor or ECU, as with those it should give no fuel AND no spark...I believe that's correct. The coil is still on my list of upgrades, [email protected], so thanks for the suggestion. First, I'd like to figure out this fuel issue.

So, I attempted to do some relay tests (brand new Fuel Pump Relay, by the way), and when I remove the relay and test between 86 and 85, I see 12V when the ignition is in "RUN", and it drops when I crank the engine (ignition in "START")...however it only drops to about 9V, give or take a volt or two... is this normal behaviour, or should it drop to 0 or close to 0? I also tested cranking the engine with the volt metre between 30 and 87, and I see voltage. It wasn't exactly showing 12V (about 10-11), but I also think my battery is getting a bit low from all the cranking attempts... so I have to charge it up.

In a nutshell... it seems the relay isn't a problem. At this point I think it's either a bad fuel pump, or bad wiring to the fuel pump (I'm hoping it's the former). That brings me to another question. If I test the voltage at the two leads for the fuel pump when cranking, should I see 12V? I'm assuming so.

To answer downhiller's question... it usually takes at least an hour, sometimes more, before it will start again. It seems it has to completely cool down. As I've mentioned before, I think I have several issues that are all working together to make this confusing. I think the no-warm start is caused by the temperature sensor (yet to be replaced, but I have the new one). I think the fuel pump is also sporadically stopping. I had it out a few days ago, and just after playing with it, the car worked quite well for a few days... but now it's not cold-starting either. Again, I think that's the fuel pump.

I'm hoping that new coil, new temperature sensor, and new (used at first) fuel pump will resolve all of the problems. I don't want to "throw parts at the problem", but it seems that the symptoms are consistent with at least a couple of those culprits. The no-start when cold should not be caused by the temp sensor, seems to be the fuel pump as per last night's tests. The no-start when warm seems it may be caused by the temp sensor, as it's too coincidental that the fuel pump fails EVERY time it's warm. Hard to say though.

Appreciate everyone's continued help and input. I will keep you posted.
 

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You can jumper pins 30 and 87 in the Fuel Pump Relay socket...should make the fuel pump run continuously as long as ignition is ON....you should be able to measure 12 volts across the pump then.
 

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Discussion Starter · #11 ·
Hi [email protected],

A quick question about the twist-lock connector you're referring to. I do see it, but haven't been able to check it yet. I'm planning on doing some work on the car on the weekend so I'm going to check it then... it's been raining here. If it is corroded and causing problems, where can I find replacement parts, and/or is it replaceable/repairable? I don't see a lot of "wiring harnesses" or things like that when I look at parts sites, and a lot of stuff from BMW seems discontinued. Thanks!
 

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Bavarian Autosport
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Hi [email protected],

A quick question about the twist-lock connector you're referring to. I do see it, but haven't been able to check it yet. I'm planning on doing some work on the car on the weekend so I'm going to check it then... it's been raining here. If it is corroded and causing problems, where can I find replacement parts, and/or is it replaceable/repairable? I don't see a lot of "wiring harnesses" or things like that when I look at parts sites, and a lot of stuff from BMW seems discontinued. Thanks!
If it's there it will be right under the intake manifold in the center pretty much inline with the throttle body. I know it's used on 89's and we have an 88 here that has it too. I think it started in 88. But I don't know for sure about a Euro IX. If it's there and it's corroded a lot of people just bypass it and solder/heat-shrink the wires together. But I'm not aware of a repair kit for the plug. As a business we tend to try not to sell wire harnesses and that's likely the only way to get it.
 

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Discussion Starter · #13 ·
Update

Hi folks,

Thanks again for everyone's help. As an FYI I did find the round connector you were talking about, [email protected], so thanks. On the weekend I replaced the intake manifold gaskets. That was something the car needed that I'm sure wasn't helping the no start issue, but I don't believe was causing it either. It seemed a bigger job than some describe it as, but I'm sure experience has a lot to do with it! Either way, it went well and I got it all back together.

I also picked up a used (but known to be functioning) fuel pump on the weekend, as I was expecting the fuel pump after a variety of electrical tests. So, last night I put the "new" fuel pump in, and the car started right up. I let it sit for a while, running, and there didn't seem to be any problems (ran a bit smoother too, thanks to the new gaskets I'm sure). After letting it run for a bit, I turned it off to see if I'd have the warm start issue again, but sure enough it started right up again. So, I was cautiously optimistic that I'd solved the problem and I took it for a little drive around my subdivision. During the drive (at this point it had run for at least a half hour, maybe 45 minutes... minus the moment I turned it off to see if it would start again), it quit on me. The engine just cut out. I pulled over to the side of the road. Tried to start it a few times...nothing. So, I figured my issue was just not resolved and the drive was just luck. I even tried a jumper on the fuel pump relay...nothing.

I went back to the car about an hour later, assuming it would start now that it was cold... but nothing. I was going to leave it for the night but then I decided to check the fuse panel, and sure enough, fuse 11 was blown (this had never happened in all my previous troubles). So I put a new fuse in, and away it went. I didn't even get the 500 or so meters to home and it quit again...fuse blown again. I put another in and made it home with that.

So... (and I'm sorry this is long, but I try to be descriptive) I now seem to have a car that runs OK, and starts when warm...but blows fuel pumps. I know that the fuel pump itself, if bad, can blow fuses, and that other common reasons are a short in a wire somewhere, or possibly clogged fuel lines (causing the pump to strain). I am going to check for shorts, but I really didn't move a lot of wires, so I can't see anything like that happening but it's certainly possible. I'm wondering if anyone can tell me what a likely cause may be, given that the car now seems to only be able to run a few minutes, tops, before blowing a fuse, when it ran for 30-45 minutes fine prior to that. Is it that most of the time prior, it was just idling? Is it that something may be causing the pump to fail? Or is it likely, given these circumstances, that it's actually a fuel line/pressure issue. The reason I'm asking the latter is that I have a new fuel filter that I haven't put in yet so I plan to do that asap.

Any thoughts would be appreciated. I think I'm getting there, but it's unfortunate that this is now happening. I plan to try putting an ammeter on the pump itself, but I need to build a little test kit first. Oh, one last question...are there different models of fuel pumps that could maybe be causing this? The one I put in looks the same as the one I took out, except for the bottom suction/filter part... it is rigid plastic on my old one, and more like a filter bag on the "new" one. I'm wondering if maybe it just draws more current if it's a different model.

Thanks!
 

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What rating is your Fuse 11?

My circuit diagram for the USA 325i shows 15 A in the fuse box diagram but then the circuit diagram shows 7.5 A?

My USA model 318i shows 15 A in the fuse box and the circuit diagram.

I am sure the "15 A" is a mistake...I will look at some other diagrams but possibly your new pump comes from a model that needs 15 Amps fuse rating.

Edit to add: The Haynes Manual, which covers European models, states that fuse 11 is a "15 Amp"....Haynes does have a lot of errors though!

Put your ammeter inline with the pump and see what it measures at different engine loads and wriggle the wires around to see if the current suddenly shoots up!
 

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Discussion Starter · #15 · (Edited)
Hi Billwill,

Thanks for the info. My fuse is 7.5 A, and that's all I've read. The Bentley manual gives three different possible pump models with the highest being 7 Amps, but that's a US book. I'm pretty sure the car it came from was a US 325iX, though mine is a European model (German). I will definitely check it with an ammeter on it (and wiggle the wires). I still have to replace the fuel filter as well. I started it yesterday evening and let it sit in the driveway for about 5-10 minutes. It has yet to blow a fuse when idling, so I'm not sure if moving the car moves stuff around enough to reveal a short, and that's causing the fuse to blow, or if increased fuel demand is revealing a somewhat clogged fuel line. Option 3, I guess, is that the pump is just dying.

Speaking of which, I recorded an audio clip of the pump running last night, and in less than 60 seconds it makes a couple of changes in the way it sounds. It sounds, for 2-3 seconds at a time, like it's getting bogged down or something. Almost like what you'd imagine it would sound like if it decide to change directions all of a sudden. I may try to post the clip to a public link so maybe someone can listen and tell me if the pump sounds normal or if that's sign of a problem.

Snow storm here... So I'm not able to do much with it today.

Thanks!

UPDATE: Here's a link to the sound clip of the fuel pump running. Listen at 26 seconds, and near the very end. It sounds to get a bit sluggish... is that normal or sign of a bad pump?
https://dl.dropboxusercontent.com/u/45024756/Fuel Pump.m4a
 

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did you get the electrical connections nice and tight?
 

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Discussion Starter · #17 ·
I believe so, the connector on the fuel pump itself is on until it clicks. I ran it yesterday a few times for about a combined hour, and I tried wiggling the fuel pump connector while it was running. I wiggled it and the wire quite a bit and there were no shorts. The fuel pump didn't cut out (fuse didn't blow) or anything like that. It seemed to run a bit smoother as well... not as much of the bogging down that you can hear in the sound clip (if anyone was able to listen to it).

I'm hoping perhaps it was a fuel tank ventilation issue causing build-up of pressure. I've heard that's possible. I'm still thinking that it could be a wiring issue though. I think the voltage readings I've been getting at the main and fuel pump relays are not what they should be... so I probably have some voltage drop somewhere. I will try to do some tests and clean up the wires as best as I can, ASAP. I haven't been able to do much with it in the past couple days as we've been hit with a snow storm.
 

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livin large
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do a voltage check on the battery while the car is running. if there isnt full voltage from the alternator, then that could cause the high amp draw.
 

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if youre under the rated voltage, the electrical load will increase the amp draw to make up for the lost voltage. it was a sperratic lazy, half buzzed, well educated hvac training response on the fuse blowing issue.

given the symptoms, blowing fuses while driving and the pump noises, fits a low voltage/bad alternator situation quite well
 
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