My L98 became increasingly hard to start in the morning. It acted like it was starting in a lean condition. Once I got it going it would run fine for the rest of the day. Putting a fuel pressure gauge on it revealed that it only pumped up to 30 pounds when the key was turned to ignition. It started, but with great difficulty. After getting it running and switching it off, the pressure would bleed down relatively quickly and I thought it may be a check valve in fuel pump or fuel pressure regulator, but this was not the problem. I elected to install a new fuel sending unit, which includes the pump, pulsator, fuel tubing, and fuel level sending parts. Cost me 280 from Amazon for a Delphi unit. This has solved the cold start problem. I did a 8 minute video of the removal and install. On youtube if you want to take a look. Not the best quality, but it may be helpful to someone. The task was really not too difficult. Keeping trash from falling into the tank was the hardest part.

steve

 

Steve...good video and explanation, thx for taking the time to do this. Glad it helped with your cold starts. Will you still change the injectors?

 

So exactly what was the leak caused by? Pulsator?

 

Nice feedback Phatphil. Thanks! I will change the injectors some time. The old injectors even though they are 25 years old still all Ohm out at 16.6 ohms, every one of them, and the car seems to run really well with them. So i don't think i have a bad leaky injector. Now that i have a pump that pumps the full 40 psi with the key turn the car starts well again.

steve

 

aklim,

I did think that perhaps i had a bad check valve, pulsator, or maybe even a bad fuel regulator. The FSM has test proceedures with regard to pinching off fuel supply and return lines if the fuel pressure does not hold. Problem with the FSM is it gives no length of time the pressure is suppose to hold.My pressure bled down to 10 pounds in perhaps 10 minutes. Don't remember exactly how quickly, but to me it seemed like it should have held at 40 for longer. I no longer think this is the case. I pinched both lines both before and after the install of the new pump and in both cases saw the same relative pressure drop. So i think i have ruled out defective check valve and fuel pressure regulator. I think what i had was an old pump that did not pump up to the full 40 psi. Could have been pulsator, but i took a good look at it and did not see anything wrong with it. The old pump topped out at 29-30 and i think that was all it took to make the car start hard. It would crank maybe 10-15 seconds and i would get one or two cylinders firing, and then the rest of them would come on board. That type of thing. It was a real struggle to get it started. Evidently 10 psi missing from the pump is a big deal?

I have read other threads regarding fuel pressure bleed down and for some people fuel pressure overnight that goes to zero is expected i guess? Taking a look at the return line i see that it discharges at bottom of tank, so air should not be able to get into the fuel rails. I would agree with other threads that pressure at zero is no issue, until the ignition is turned on and then you need 40 psi.

All i can tell you is that a new sending unit cured the hard starts. Also got a lot of corrosion out of the fuel tank too!
Best!
steve

 

Ohm test is only going to tell you the coils are within spec. Doesn't do anything else which is why I don't even bother. Every few years I send them off for testing and cleaning. I suppose if I suspect something wrong in between I may just test the coils. NFW would I rely on the Ohm test for much.

 

It's a pretty crude test to find out if the injectors are not grossly bad.

It's sort of like checking tire pressure. It may be OK but the wheel might be out of balance or the suspension misaligned.

 

Test only points out if the coils are bad. Even if the pintles are broken or plugged, it could still ohm out good. I have found that every few years I could benefit from a clean just based off the reports. Not sure why people place faith in the ohm test or "it runs great". Injector performance and balance deteriorates so slowly, it becomes hard to remember what it was like new.