Fuel Related Slow Start

[jeffnhiscars]

I reman'ed a head and got my barn find running (long story & yes I should do a build thread). Anyway, 1st time it started well but did crank for a few seconds which I attributed to it not having run in over a year. Once it fired it ran well and did fine on a short test drive considering the muffler was blown.

Next time I tried to start it and it was also a bit slow so either spark or fuel. I jumped the fuel pump relay, heard the fuel flowing so I put the relay back and it started immediately which points to fuel pressure. Since it runs ok once it starts I think the FPR is ok.

I believe the fuel pump is fired by the CPS signal going to the DME so until its running, fuel flow is managed by the starter turning the crank. When I changed the fuel filter I did remove the pulse damper and am thinking that the rail is not holding fuel pressure without the pump running. It could be the FPR but Im thinking there is a check valve or something else holding rail pressure when the car is off so it doesnt have to go through all of this cranking to start.

Any insight ?

[lcoleman]

There is a check valve, it's built into the pump. The pump itself is triggered by the DME.

I would check pressure with a gauge. Since it runs fine and doesn't die, my money is not on the pump, but the regulator itself. Also check the vacuum line running to it, of course.

[jeffnhiscars]

The vacuum line is new as are all intake manifold seals, fuel lines etc. I'll try swapping FPR's with my 89 and see if the problem follows it. In the meantime here is some eye candy.

[rasputin]

crank postiion sensors are cheap, so might as well throw one in, but i'd bet you have low fuel pressure on start ups, get a fuel pressure gauge and test it. could be a leaky injector or something of the sort, even a possible clogged/partially clogged injector.

[jeffnhiscars]

I can also swap the CPS if the FRP swap doesnt reveal the problem. As for the injectors, they got the royal treatment from new filters & pintle caps to repainted bodies. I dont think even a bad one would be causing this problem.

[lcoleman]

Is this car an early model with a lift pump? It just occurred to me; that could be an issue as well. Not as likely, though.

I shouldn't be helping, since this car is an automatic. :p

[jeffnhiscars]

Is this car an early model with a lift pump? It just occurred to me; that could be an issue as well. Not as likely, though.

I shouldn't be helping, since this car is an automatic. :p

Transmission won't effect starting but it is 4\87 production with 2 fuel pumps. I believe they both work since the sound of fuel circulating is normal when jumping the fuel pump relay. I wonder if the internal check valve mentioned above is bad.

[oldmann]

If the CK valve on the pump has gone bad, you can install an inline CK valve.

There is one available from BMW for less than $10, P/N 16 14 9 068 988,

It goes in the pressure line close to the pump, 2 hose clamps and done.

Was a retrofit for E34's that had CK valve failure.

Have the parts guy ck the P/N, most don't know this thing exists.

[jeffnhiscars]

I removed the device that was installed inline at the pump\filter since it looked crap and I understood it to be a pulse dampener which was not essential. Perhaps not the same part you refer to.

I may add that to the list of swap/reinstall widgets.

Note: FWIW the part I removed is #17 "absorber" & I dont think it is the problem. The PN you provided did not show up on realoem but I do believe there is a BMW check valve

http://www.realoem.com/bmw/showparts.do?model=BB23&mospid=47326&btnr=16_0181&hg=16&fg=15

[jlevie]

If the high pressure pump and FPR are working correctly the rail will go to full pressure within a few turns of the engine even if the rail has no pressure at all. In most cases, when the check valve in the high pressure pump is bad the pump is pretty worn and not able to deliver full flow. You can, in a case like that, add a check valve, but doing so just delays the inevitable replacement of the pump.

[oldmann]

I removed the device that was installed inline at the pump\filter since it looked crap and I understood it to be a pulse dampener which was not essential. Perhaps not the same part you refer to.

I may add that to the list of swap/reinstall widgets.

Note: FWIW the part I removed is #17 "absorber" & I dont think it is the problem. The PN you provided did not show up on realoem but I do believe there is a BMW check valve

http://www.realoem.com/bmw/showparts...81&hg=16&fg=15

The part I showed was from a recall done on E34's, will do the same job

as the original built into the pump.

I've never seen the part listed anywhere but a dealer.

[jeffnhiscars]

I popped a muffler on today and Im amazed at how quiet it is. I do have 1 loose valve but other than that I do not even hear a sewing machine.

As for starting, it seems to be hit and miss and uneffected by whether its stone cold or has run in the last few minutes. That sure does not sound like a check valve or even an FPR so Im now starting to think CPS.

Can they behave like a bad starter solenoid where if they work or not depends on whether they stop on a bad spot & is bench testing them reliable ?

FWIW I got a Bosal from..of all places..Amazon. 1 day overnight on my Amazon Prime for $199 plus another $45 for the hanger kit which included 4 donuts. I'd say thats not too shabby.

...and I agree with you Jim..no sense in adding a check valve to compensate for a tired pump although w 98k I now doubt thats the problem

[lcoleman]

1. I know trans doesn't affect starting, I was giving you grief for having -1 the correct # of pedals.
2. That absorber is not crucial, I haven't had one in years.
3. Low miles on original pump means it has probably sat for an extended period at some point in its life, which is bad for pumps if there's ethanol in the gas. I still think the transfer pump could be bad, you need to pull the rear seat and see if you can feel it working when priming and/or running.
4. You are taking shots in the dark until you get a proper fuel pressure gauge and test it. Losing pressure after sitting points to fpr or a bad pump check valve, more likely the fpr in my opinion.

[jlevie]

...and I agree with you Jim..no sense in adding a check valve to compensate for a tired pump although w 98k I now doubt thats the problem

Mileage is certainly a factor, but history matters also. It the car has sat idle for extended periods with a partial tank, water could have accumulated and rusted the tank. Rust will kill a high pressure pump in short order. I've seen E30's with less than 100k on them with rust damaged pumps.

[jeffnhiscars]

1. I know trans doesn't affect starting, I was giving you grief for having -1 the correct # of pedals.
2. That absorber is not crucial, I haven't had one in years.
3. Low miles on original pump means it has probably sat for an extended period at some point in its life, which is bad for pumps if there's ethanol in the gas. I still think the transfer pump could be bad, you need to pull the rear seat and see if you can feel it working when priming and/or running.
4. You are taking shots in the dark until you get a proper fuel pressure gauge and test it. Losing pressure after sitting points to fpr or a bad pump check valve, more likely the fpr in my opinion.

I like grief..so bring it :)

yes the car sat...for about a year with a bad TB & the tank quite low so no way to know at the moment. I'm about to fill it so that may change something.

Shots in the dark go with grief...but my next step will be to swap the FPR from my 89 to resolve that question.

Mileage is certainly a factor, but history matters also. It the car has sat idle for extended periods with a partial tank, water could have accumulated and rusted the tank. Rust will kill a high pressure pump in short order. I've seen E30's with less than 100k on them with rust damaged pumps.

Again when I jump the relay I can hear the fuel flowing and then the engine starts right away every time. My gut tells me its not the pump but I've been wrong before.

We shall see.