polecat702

My 89 has been running fine for a week. Today it got hot again in Vegas. Was on the Fwy, almost home, bout 5 miles away. Started acting like it wasn't getting any gas. Miss fired died and started running, then died, and wouldn't restart.

Let it sit, bout 30 mins, and restarted. Took off for the house got maybe 3/4 mile, and died again. Pulled in to the Texas Casino parking garage. Parked in the shade, went to a movie, so it sat bout 2hrs. Came out fire right up. Died again, bout 1/2 mile from home, let it sit about 10 mins. Started and got it in the garage.

I've replaced the internal fuel pump, external pump, new filter, plus hardware. Pressure regulator, temp II sensor, CPS, Hall Sensor. New relays. New battery, 200 amp alternator.

I checked the fuel dampner, at the rear of the motor, it held vacuum, ( ordered a new one from Roger, he sent the wrong one, will return.) It's supercharged, and doesn't use the front dampner.

I ain't worth a hoot on electrical, but trying to learn.

Any ideas, are greatly appreciated!!!!!!!!

Thanks all.
joe

Mrmerlin

Hi JOE are you sure you put in a fuel pressure regulator on the right rear fuel rail pass side the Center front damper and rR part look the same
check your charging system maybe it's overcharging too much volts will shut off the computer or fry them

FredR

Friend of mine over here had similar symptoms with his 87. Put my spare LH in his car problem disappeared.

Not saying that is your issue but something to be eliminated from the line of enquiry.

polecat702

Stan, it's charging around 13.4 volts. It never goes up or down Idling in traffic, A/C on, or on the fwy. Stays the same.

I checked the part numbers and matched them up, because I've read of people switching them. I don't have the one that goes in the front of the engine. I need the one that has the three lines coming out of it and the number ends in 034.

polecat702

Fred,

I can send mine off to Louis Ott, in the morning, and get it back here over night. I've never touched the LH, other than changing out the chips for the supercharger set up. I don't have any idea if it was ever rebuilt by the PO's.

I was under the impression that when the LH died, it just crapped out, car wouldn't restart, it was dead. This is intermittent. I'll do it, probably needs it anyway.

FredR

The common LH failure is when the fuel pump does not kick in but that is not the only failure mode. Indeed when my friend's unit crapped out I understand it was a failure John had not seen previously and apparently there are a number of failure modes that are less common but nonetheless do happen. Best thing is to transplant your LH into another 928 and see if the problem migrates.

Whether or not this is the root cause of your problem remains to be seen but it sounds suspiciously like the symptoms my friends 87 S4 presented. We put my spare LH into the car and the problem disappeared immediately.

Just keep an open mind at this stage until you pinpoint the issue.

Rgds

Fred

Tony

relays going south?

polecat702

All the important ones are new. Cleaned the panel too.

polecat702

I guess it's common knowledge that the LH, goes south on these cars. I'll just send it off tomorrow, and be done with it. I figured, I'd have to do it anyway, sooner or later.

worf928

Grounds. Connections. Harness condition.

Battery ground strap. Tight? Good condition?

Battery positive connection?

LH grounds at the back of the block? Have these been 'messed' with?

Overall condition of LH harness? Brittle? Any splices?

You're right that the problem is 'lectrical.

The trick, now, is to figure out how to reproduce the problem at will.

What I would do: wrap the ends of three lengths of brass safety wire around the end of each of the LH engine grounds and the harness at the CPS connector. The wire should be long enough that you can get to it once everything is back together.

Start the car and then in sequence push, pull and wiggle around each of your three lengths of wire. You're trying to see if you've got a harness break or loose connection. If you wiggle a wire and the car dies you've found your problem.

Coat hanger will work if you don't have safety wire, but it's almost too thick to work with.

polecat702

I've got the wire, and I can do that. Thanks Dave!

worf928

You're welcome.

If though your Lh hasn't been rebuilt, then just get it done. It's going to fail. Do that and then worry about harness unless you already harbor some harness suspicions.

polecat702

I'm the 3rd owner, as far as I know it hasn't, so it's off to Louis tomorrow.

Thanks for all the help!

Chalkboss

Good luck finding the problem Joe, sounds like you are on the right track. I have a related question:
In the 4 years I have had my 87 I have not messed with the LH, and while I have extensive past records I am missing a few years. Is there a way to know if the LH has been rebuilt? A sticker??

worf928

Yes. AFAIK, all the rebuilders put a sticker on the back side of the LH.

To get to this backside, you have to remove the whole 'brain case' and then unbolt the LH from the case.