Please Help. '87 325is running problems.(update)

[NeedaBimmer]

I know their has been a plethora of threads about people's engines cutting out or stalling. But since this can be caused by many things I felt the need to post my own thread.

THE PROBLEM

The car, 1987 325is, will start ok (it cranks for a second then starts, I think it might be trying to gain fuel pressure.) then it will pull fine in first gear and ok in second until 2k-3k. Thats when it will normally sputter and sometimes dies. But if it makes it past 2nd the same thing with just happen in third or fourth gear.

When it sputters/hesitates the tach doesn't move and the econometer doesnt dive to 0. But if it flly cuts out and dies, the "check engine" light comes on and the revs slowly fall to zero.

Basically I'm wondering if it's a fuel or electrical problem.
I have done several test on sensors, fuel pump, ect.


This is what ive tested/replaced

• main fuel pump flow test: was off by a little but not enough to worry me. It is also whining a dog.
• Intank pump was replaced by previous owner around may
• new spark plugs (bosch copper cores)
• new cap and rotor
• new ignition coil
• cps read 550 ohms
• new main relay
• new fuel pump relay
• afm tested fine
• injectors cleaned, plus new filters, caps, and seals
• fuel rail cleaned
• valve adjustment
• tps tested fine
• grounds read fine
• fuel filter
• air mass meter boot

I cant remeber if I tested the ecu but im going to test that, o2 sensor, and coolent temp sensor as soon as I can.

I'm running out of money and don't have a lot of free time between school/work. So I would really appreciate any help or suggestions on what to do next.

Thanks for your time.

[jlevie]

Check the rail fuel pressure while driving the car.

[NeedaBimmer]

I havn't had time to check the pressure yet. But how do I check the pressure while driving? All I see in the bentley is how to check system pressure and pressure under load.

Thanks for your time.

[jlevie]

Tee a pressure gauge into the line that feeds the rail. Zip tie the gauge to the windshield wiper where you can see it while driving.

[NeedaBimmer]

I finally got a fuel gauge and tested everything except the pressure while driving, it's too dark to do that right now.

During the system preasure test it would read what appeared to be 46-48psi and didnt change while clamping the fuel return line.

When I did the under load test it was reading around 38psi while idleing. When I removed the fpr vacume line it shot up to 46-48psi. Finally while reving in neutral it would shoot up to 46-48psi then fall dramatically to 32-34psi and return to 38psi. During all the test it never exceeded 50psi and never went lower than 32psi.

I'm not quite sure what to replace, any help interpreting these results would really be appreciated.

jlevie, should I still do the driving test? I feel like the preassure would act the same as it did while reving it in neutral. But if you think the results while driving would make a difference in what to replace I'll do it asap.

[Ceeker]

I know you said the intank pump was replaced. But check the pressure again; it could be faulty. you may just lose fuel pressure when the demand for fuel increases.

[delatlanta1281]

is your outboard fuel pump whining whith a full tank of gas?

[NeedaBimmer]

Yes. The external main pump has been whining since I got the car. At first I thought it was just my filter bumping the mount but now I know it's the pump itself.

I'm going to check my transfer pump once I get a fitting for my gauge.

[jlevie]

I finally got a fuel gauge and tested everything except the pressure while driving, it's too dark to do that right now.

During the system preasure test it would read what appeared to be 46-48psi and didnt change while clamping the fuel return line.

When I did the under load test it was reading around 38psi while idleing. When I removed the fpr vacume line it shot up to 46-48psi. Finally while reving in neutral it would shoot up to 46-48psi then fall dramatically to 32-34psi and return to 38psi. During all the test it never exceeded 50psi and never went lower than 32psi.

I'm not quite sure what to replace, any help interpreting these results would really be appreciated.

jlevie, should I still do the driving test? I feel like the preassure would act the same as it did while reving it in neutral. But if you think the results while driving would make a difference in what to replace I'll do it asap.

The pressure not changing when you clamped clamped off the return line is one symptom of a bad pump. The pressure should have gone up towards 80-90psi. The drop in pressure while reving the engine is another symptom of a bad fuel pump. And the noise from the pump is a sign of a bad pump.

Make sure the in-tank pump is working and replace the high pressure pump and fuel filter.

[NeedaBimmer]

jlevie, thank you so much. I hope that will fix it.

Also the bently says that at 68*F the transfer pump should be around 4.3psi. When they say 68*F do they mean the fuel temp or outside temp? Because it's 91*F right now, will this affect the fuel pressure reading a lot or only slightly?

[jlevie]

The flow rate of the transfer pump is more important that the pressure. It's only job is to lift more fuel to the high pressure pump than the flow through the system demands. As long as the high pressure pump isn't being starved for fuel the system will work as designed. Anything from 2-5psi from the transfer pump will be fine. Wear in the transfer pump hadly ever is a problem. But wear in the high pressure pump is always a problem. The most common problems with the transfer pump are total failure or rust in the tank clogging the inlet screen.

[NeedaBimmer]

sigh..

So I put the new pump on and everything went fine.

When I did the system pressure test the pressure was in the right range (maybe a little bit high) and it raised when I clamped the return line( but it didn't raise by much).

But when I did the test under load the pressure still reads under 40 psi while idleing and will drop while reving.

The pump didn't whine at first but after 10 or so seconds it started to whine but not as bad as the old pump. I also can't tell if the intake pump is whining or the main pump is.

So do you think its the in take pump, fpr, or what?

Can I flow test the intake pump the same way you test the main pump?

Can the problem I'm having with the fuel pressure only be caused by the in tank pump and fpr? Because the more I think about it, I'd just buy both so I dont have to deal with it anymore. I hate not being able to drive it.

[NeedaBimmer]

I think I f**ked up.

Ok, I was trying to test the amps of the intank pump and after I jumped the relay I go to check what my meter is reading. But instead of seeing the reading I see a spark come from the left prong of the intank pump electrical conector so I move my test leads and remove the jump wire. Now if I jump the relay nothing happens.

Did I just ruin the intake pump or did I do something worse?

I'm going to pull out the intank pump soon.


Pulled the intank pump, found rust in the tank.

Not the happiest person right now.

[NeedaBimmer]

Got the car road worthy again. I basically replaced everthing related to fuel delivery except fuel lines and hoses,. I'm just glad I can drive it again.