Eturbo924

Ok have had issues with a failed fuel pump... replaced it only to have the car stall on me not 40 minutes of running later. More specifically the car refused to start when I first put the pump on. Then after taking the car down off the jack it started right up. The next morning I took the car to work and then on an errand. It ran perfect... better than ever. Then about 1 hour later I took it to lunch... 10 minute ride. Had 1 hour lunch and came out to the car. It started right up but only made it 200 yards and it just shut off. No chugging... no sputter... just off.

I read many posts about 928S4 failing to start relay issues, crank sensor issues (connectors seem to go bad) and failing LH computer.

I read that a "clicking" in the motor is a good indicator that the LH is on its way out or dead. What exactly does this clicking sound like? More to the point. My car when the ignition key is turned to the run position has a click under the hood. It kind of goes click click and then a brief sound like some thing is energizing. Is this the bad "click" or is this normal and the failure mode click is a constant one?

Also could this same clicking be caused by a bad crank sensor (or sensor connection)?

I swapped relays all over... horn one to all that match it. No change. All make the horn go so I assume all relays are good. I did note some corrosion on one of the terminals of the relay block. I put the relay in and out a couple times in hopes it would help. I can not recall the fuction of this one but recall it is the upper right most relay.

I have a lot of tests to run but I hope to eliminate the LH from the group.

Anyone know of a 1987 928S4 in the NH/Mass area that might be willing to loan me the LH so I could test my car... and or I could put mine in theirs?

Thanks

Eric
Oh just in case mine is a 1987 928S4 auto 118K miles.

Landseer

Switching relays in panel is not a definitive test, I've found. Depends on the voltage pulling-in the relay in each separate postition on the panel. So a relay working in one slot might be non working or intermittent in another slot. Use jumper wires to test. Don't write-off the brains yet.

What's the history on this car?

Last time you had CE panel out for cleaning? Various grounds around car cleaned?

WallyP

First easy, free test - have someone operate the starter while you kneel by the back bumper listening for the buzz of the fuel pump. If you have no buzz, the car won't run.

If there is no buzz, first replace Fuse #42 - even if it looks perfect, replace it. Check for the buzz again.

If still no buzz, pull Relay XX (fuel pump) and install a temporary jumper between terminals 30 (power) and 87 (load - in this case, the fuel pump). With this jumper in place, the fuel pump must run. See if the car will run.

Let us know what you find - in excruciating detail!

Eturbo924

CE pannel? :-)
I have not cleaned the grounds. I did inspect them tonight... they look clean and bright up above the area in the fuse/relay block.

This car has been a pain in the butt!
Ran perfect most of its ride home in the spring (purchased it in NC). But in NYC it started to have a surging at idle issue. It was fine driving but surging to the point of almost stalling at idle speeds.

Got it home... found MAF was loose and replaced some bad vac lines, cleaned negative lead strap for battery, changed oil and filter and spark plugs. It ran well enough for 1000K miles or so. But the idle was high 1100 or so. Then it started missing slightly and hesistating. So I got back into it and found the wires from the coil to the disty caps were wrong. They had two female sides... thus the sides that went into the coil were badly corroded.

So I replaced the wires and cleaned the corrosion out of the coils. Once again she ran decent. I took it down to CT (from NH) this past weekend. It ran quite well... not perfect but good as I had it to that point. Then returned home Sunday night and Monday morning it would not start. Monday night I determined it had a bad fuel pump. I put power to the pump and it would just barley move and die. So I replaced it. As I said above it would not initially start. So that is when I moved relays and such around... so maybe I moved a bad one into a position that it really did not like.

Anyway I could not get it to start. So I gave up... put my tools away and took it down off the jacks. Then I crossed my fingers and turned the key. Bingo it started. I shut it down and started it a couple more times and it was perfect. and then we get to the rest of the story that I started with above.

Mrmerlin

if the key in the run position prior to cranking gives a clicking noise under the hood then its probably the fuel injectors, this mean the computer needs to be rebuilt, the other test is to see if the tach jumps when the engine is cranked, this indicates a good crank position sensor, and a good computer

Lizard928

CE Panel is Central Electrical panel. AKA fuse panel.

The clicking is obvious. Though not all failed brains click. So if you do not hear a loud click click click with the key in the run position and not cranking. Then jumper the FPR and see if you can hear the pump running.
I would be putting your brain into another car and trying it out as quick as possible. Or buy the brain the Giovanni has for sale.

John Speake

As your car seems to run, then not, I would not suspect LH ECU at this point. They rarely fail intermittant.

Sounds more like a fuel flow problem to me.... but you need to work methodically through.

When car won't start, do you have spark ? Does trach flicker when you crank the engine ?

Do you hear the FP at the rear run when someone cranks the car for you ?

Landseer

On this car I would clean the ground strap, passenger side, under car, linking block to frame.

Then, the two ground wires that are mounted to the clamps that hold the coils.

Then, pull the CE panel and thoroughly clean it and those two sets of groundwires above it mounted to the firewall. Probably replace all 45 fuses if corroded at all and clean relay contacts.

Solves a lot of problems like this.

cold_beer839

Also, does it happen after you wash the car or drive in the rain? If so make sure the big harness connection in the engine bay (just behind radiator on passenger side) is not getting wet due to a cracked or missing cover. Probably wouldn't hurt to open it and clean it also.

A sure way to test the LH ecu is to put it in another car, or put a known good LH ecu in yours. I had to replace the one in my '87 after putting in AA chips (they are fragile as hell). I got a reengineered LH ecu from John Speake at JDS Porsche, and I'm telling you the car run better than it had before with the old original LH ecu.

Eturbo924

Thanks for all that information... makes me less likely to jump off a cliff now.

Two quick updates to see if this helps.

I put a timing light on the car last night. Figured it would be an easy way to see if the car had spark. I tested one wire from both disty. I got flashes from both sides. So this would mean I have spark.

I removed the cover for the fuel pump and fuel filter and jumpered the FPR. I could hear the pump running and then tried to start the car. Nothing...

Oh and the night I replaced the fuel pump. I pulled the fuse for the fuel pump and noted heavy gray corrosion on it. So I cleaned it off and put it back in.

More information on the day the car died... when I cranked it the tack jumped up a couple hundred rpm at first then down to zero. I do not recall for sure because I was not really watching for it... just noted it. So does it falling off in height mean anything?

So we have that the pump runs when jumped (only time I could know for sure it was on... when car is cranking I could not hear it even when jumped... and did not have anyone at the time to listen while FPR was in). Timing light seems to indicate I have spark. The tack jumped when turning car over... if just for a bit.

I will print out all your suggestions and be back on it when I return from vacation. It is going to be killing me the whole time thinking about what I need to test but fire away if you have other thoughts now.

Thanks everyone.

Eric

Eturbo924

Oh and rain does not seem to effect it.

Eturbo924

OK quick update. Tach pulses and continues to pulse... had the wife do it :-). So that checks out.

So tach pulse, fuel pump jumpered and timing light shows spark. Still no start.

Mrmerlin

Go to the CE panel and pull all of the fuses and clean them with a pink eraser, also remove the ground wires connected above the CE panel( brown) and the power wires ( red) that are connected to the top of the CE panel and do these.
Also pull the relays out and inspect every one make sure that they are the correct relays for the position (www.928gt.com for a fuse panel relay chart)
Remove the hot post connection and the 14 pin connector and inspect/clean these as well , make sure you have a hot post cover fitted. If you

John Speake

Have you swapped out the LH relay XXV for a known good one (or jumpered it) ?

Eturbo924

The only relay I jumped was the FPR.

I believe I did swap that one with the horn relay. It did work fine in the horns position as well.