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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series / 4 Series > E30 (1982 - 1993)

E30 (1982 - 1993)
God's Chariot. The E30 was produced primarily from 1982 through 1991. The cabriolet was the one exception which was produced through 1993.

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Old 01-27-2014, 11:27 AM
usna1974 usna1974 is offline
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Location: Virginia
Join Date: Oct 2013
Posts: 11
Mein Auto: 1986 325E Sedan
Cold Start Problem Diagnostics

1987 BMW 325e automatic transmission.

Was given this car about 4 months ago. Since the weather has gotten cold, the car is difficult to start (usually takes 5-10 secons to start, sometimes I have to turn the key off, wait a few seconds, and recrank.). Idles a little rough for a few minutes, but no wild osciallations in the tach. After the car is warmed up, it runs great - power is strong, idels smoothely, gas mileage >31 mpg ont he highway, no misfires, etc. also, when the car is garaged at 45 degrees or higher temperature, the problem, if not all the way gone, is much less. Even on first start of the day...so this SEEMS to me to be a problem isolated to the cold start system...but I could be wrong...

This car had a rebuilt engine put in it about 5,000 miles ago. Tehr eplacement block had 100,00K on the engine, but timing chain,e tc. were changed at the time.

One other glitch that may or may not have anythign to do with the start issue. The coolant termperature guage on the dash "sticks" at full cold. If I tap it after the power is on, it will unstick, and then all operations are normal.

Anyway, I have the Bentley book, and it describes how to check the cold start mechanism, i.e. check the cold start valve, thermo-time switch, coolant temperature switch,a nd coolant temperature guage.

Now to my questions:

1. Is there soemthing else I should check first, and if so, in what order should I check those things?
2. Is it really as easy to check those various sensors and switches as Bentley describes?
3. If all sensors and switches check out OK (plus anything that I would check based on answers to the first question), what is the next step (besides taking the car to a shop)?

I would just take it to a shop, but in checking, they charge >$100/hour for labor, and they grossly mark up their parts prices (the price they quoted for a brake master cylinder was over $400. I got the exact same one online for ~$150). I can get a replacement cold start valve on line for about $130 (that is the most expensive of the switches and sensors), but anticipate they would change me in the $300-400 range - I do not mind payinf for labor, if it reasonable, but do not appreciate being gouged on the parts...they also would not install parts that I do not buy from them. when I changed the master cylinder, my total costs, including fluids, was under $200, if they ahd done the work, it would have been over $700...and the brakes are tight now!)

Any help would be appreciated. usna1974@cox.net
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Old 01-27-2014, 09:32 PM
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downhiller downhiller is offline
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Location: des moines
Join Date: Oct 2007
Posts: 6,690
Mein Auto: 2012 hypermotard 796
cold start valve would be the first place i would go.
I know a lot about cars. I can look at a car's headlights and tell you exactly which way it's coming
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Old 02-05-2014, 06:09 PM
x98agw x98agw is offline
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Location: Halifax, NS, Canada
Join Date: Jan 2014
Posts: 18
Mein Auto: 1988 325iX Touring
DISCLAIMER: Double-checked after writing that, and I see you have a 325e...which means you have the 2.7L engine. Everything below should still apply, but you should confirm on your car before you try anything. I was assuming the 2.5L engine...but good luck regardless!

Original Message:

I've had cold (and warm) start problems recently with mine, and they turned out to be separate issues. My cold start issues were caused by a failed fuel pump. It would work now and then, but when it wasn't working the car wouldn't start at all. Many report the engine having to crank over for a longer period before starting, but that wasn't my issue. My warm start issue was my coolant temperature sensor.

So, having said that. Given your issue, here's what I would check:

- Fuel Pump - make sure it's turning on. I doubt this is your issue since it sounds like it is starting after cranking over, but you can jump pins 30 and 87 on the Fuel Pump Relay to start it (with key off)...standing at the engine with the hood open you should hear the pump fire up. To jump it, remove the Fuel Pump Relay and look at the bottom of it...you'll see the pins are numbered. Jump (with a piece of wire or something) the slots that correspond with pins 30 and 87. There's lots of information elsewhere online about testing the fuel pump, so you should do some further reading first.

- Fuel Pump Check Valve - this sounds like it may be your issue, to be honest (or one of them, you may have more than one issue like I did). The fuel pumps in the e30's (the pumps in the tank...yours may have the inline pump since it's an 87, but I'm not sure) have a check valve built into them. This is to make sure the fuel doesn't all flow back into the tank when the pump is not running. These valves eventually fail, so the fuel line is essentially empty, and you have to wait for fuel to reach the engine before it will start. There are two options to fix this: 1) Buy a new fuel pump assembly, which will have a built in check valve ($200+ depending on where you live). 2) Buy a check valve and splice it into the line somewhere near the pump (sample here: http://www.pelicanparts.com/BMW/cata...TD028_pg14.htm). The second option is makeshift, but it should work...assuming that's your issue.

- Lastly is the coolant temperature sensor. My issue was that my coolant temperature sensor failed and was telling the motronic system that my car was COLD when it was actually WARM...so that was causing my warm start issue because the car was acting like it was cold (and sending lots of fuel) when it didn't need it because it was warm - thereby flooding the engine. That's the opposite of what is happening with yours, but I'm wondering if the temp sensor is maybe always thinking it's warm, so not enough fuel is being delivered on cold starts. I'm not sure, but it's a possibility. FYI there are two coolant temperature sensors mounted close together, near the thermostat housing, just under the fuel pressure regulator... the blue one is the one that feeds the motronic system, the brown one feeds the temperature gauge on the dash. The blue one is the one I'm talking about. If your colours aren't the same..the blue one is the one slightly more to the back/left of the car.

- Having said that... one more... your fuel pressure regulator could also be bad and letting more fuel go back down the return line than it should.

Sorry for the long note...hope it helps. As most say, troubleshoot and diagnose...don't just throw parts at the issue. There's lots of good threads in forums about this issue, so I'm sure you'll find the answer soon.

Last edited by x98agw; 02-05-2014 at 06:14 PM.
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Old 02-06-2014, 02:06 AM
Billwill Billwill is offline
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Location: South Africa
Join Date: Oct 2009
Posts: 480
Mein Auto: BMW E30 318i 1991
I would first change the Blue temperature sensor mentioned above^^^^

Best to first measure it at the ECU connector in case there is a wiring problem....should measure about 3,000 Oms when cold and about 300 Ohms when hot.
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cold starts, fuel system

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