Entropic86

So on one of the first hot days this year I drove about 50 miles without a problem, shut the car off, and it would not restart. The fuel lines were soft and didn't have any pressure or fuel coming out of the return line while cranking it. 3 hours later it still wouldn't start. The next day it started up and ran fine just fine. The next time the car was left idling for a few minutes, it started to stutter along at a 200rpm idle and have very poor power up until about 2200rpm. Above 2200 rpm, it would take off suddenly and accelerate like normal....I got some funny looks for driving around in first gear to get home that day. I thought the problem was heat soak / vapor lock, because it was always fine as long as I kept the car moving.

So now the problem started to occur consistently, and whenever it started to sputter along at a 200rpm idle and have really poor power below 2200rpm, it wouldn't restart after being turned off until it sat and cooled down for 5+ hours.

So I replaced the fuel relay, that didn't fix the problem.

I heard that this problem could be related to the fuel pump resistor. Someone here on CL said that they just put a jumper across their resistor and drove the car around like that. So I thought it was safe to try this: I heated the car up until the problem showed up, and put a jumper across the resistor. The car revved up to a normal idle and I thought the problem was solved. I didn't run the car for more than 5 seconds with the resistor jumped.

I ordered a new fuel pump resistor from Sewell.

I drove the car the next day before the new resistor got here, and the check engine light came on right from when I started the car. It has never come on before. I think something may have been damaged when I jumped across the resistor, but that day I drove it about 40 miles with the CEL light on. It is throwing codes:

P0300: multiple cylinder misfire. ( It listed 5 different cylinders)
P0172: Bank 1 lean condition

So the resistor arrives and I think I'm going to throw it in and all my problems will be solved....the car won't start, with or without the new resistor(it just cranks over). Right now, I'm all out of ideas.

I don't think it is related to the trunk hinge wiring issue I've heard of.
I checked all the fuses related to ignition/efi.
I hope it's not the fuel pump as I've heard they rarely go bad.

So I've come to you knowledgeable folks for help. Thanks in adavance.

As always, I'll put up a post on how I solved the problem, when I do finally solve it. I Can't wait to have a my reliable LS back!

GS4_Fiend

iTrader: (22)

check fuel pressure and check for vacuum leaks.

kayuwong

This is your ECU, I had exact problem like yours last week. Symptom is missing fire, start and die immediately, running rich on fuel, you can see exhaust manifold glowing red. Luckily I could find an exact ECU at local junk yard. Plug in and run perfect. I openen out my old ECU and found one capacitor is blown (C831). You can either try to find a used one or replace the bad capacitor on yours. HOpe to help out other LS owner around here. Good luck.

kayuwong

One more symtom, when you have a bad ECU, your A/C will not blow cold air at all. Once good ECU is in, engine idle perfect and AC works again. Good luck.

Entropic86

I tried bridging the FP/B+ terminals in the diagnostics box. I didn't see the screw on top of the fuel pressure damper move at all. I'm not sure if that counts as checking the fuel pressure....

I also hear a sucking noise coming from what seems to be under the intake manifold...I checked every hose around and didn't find any problems. A leaky gasket on the manifold somewhere could be letting in unmetered air...

The car did start again but now the power is weak right away, until about 2000rpm.

Entropic86

My A/C works fine. I'll have to rule out a number of other things before I go replacing my ECU. There are too many things that could cause this type of problem and from your description, you were not having the exact issue I am. Thanks though, I'll keep the ECU in mind as I figure this out.

mspearl95

have you thought about a clogged fuel filter or pickup screen?

Entropic86

I have thought about that, but I've dismissed it until later since it runs and gets worse as it warms up.

Entropic86

So, I've been putting off fixing my car for a couple months now.....

I pulled the rear seat to test the fuel pump and....guess what, it's dead.

Hopefully this week I get a new one in there and everything goes back together smoothly.

I think I'm going with a Denso replacement off ebay for ~$120

Entropic86

Yup, the new fuel pump fix her right up!.

My suggestion to anyone experiencing similar problems is to check the fuel pump resistance first. Just remove the liner to the front part of the trunk and check for continuity in the connector. Really easy!

1JZPWRD

iTrader: (59)

Glad you got it going again..

hotdawwg

Glad you fixed it!

Entropic86

After driving my backup (old ford pickup)...it's good to be back driving the LS.

1JZPWRD

iTrader: (59)

I bet. Nice looking LS!! I also have a backup, 1985 Dodge Ram 50 Royal Edition. Even has tilt, manual of course.

bdruff

Haha.. same color and same problem. I'm getting ready to swap the fuel pump now but I'd like to check the resistance first if I can.
I've already swapped the resistor and the relay, both with no change.

I didn't find the diagnostic box to jump the f and b+. If there is one, I haven't found it. It's an OBDII and there is a little white circular diagnostic port and the trapezoid code reading box.

Its not too tough to swap out the fuel pump but I was trying to check it first.