kevinduffy

I have a 1988 924S M030 with a lot of miles, a lot of replaced and refurbished parts and a lot of love that has been my daily driver and track car for many years. As such, once in a while it decides that it needs some time off, and stops running. Vacation normally lasts only a couple of days while I diagnose the issue and get the proper parts to make it all right again. However, this time it is taking an extended vacation.

In the past I have had the typical reference sensor connector problem. I replaced the connectors with Lindsey Racing parts, and all seemed well for about eight months. The sensors were new a few years ago, and I am running the correct DME and AFM for the 88 engine.

A few weeks ago, I stopped out at the mailbox and when I got back in the car and started it up, the engine ran at an idle for about seven seconds and then just shut off. My wife brought the truck out and we towed it back to the house. Crank, no start and no tach bounce. So I figured that the harness for the reference sensors had finally gone south, ordered a harness from Lindsey and installed it when it came in. It ran for a couple of minutes, then shut off. https://rennlist.com/forums/graemlins/bigcry.gif

Since then, I have replaced:

I also took a DME relay and jumped it as in Clarks Garage, and got it to start with it...then replaced it with my new relay, which worked fine for about ten minutes, and it shut off.

What I have not done is re-index the sensors to be sure that the spacing is correct to the flywheel. That is next on the list, but it has run for four years with no issues since installing this engine. The bolts to the sensor mount are tight, so I don't think that it is an answer.

There is an extra ground strap from the battery to the head. I do not see a ground strap going from the engine to the bell housing at all, but then again, it has run fine for years with the current setup.

I have been working on these cars for decades, and this one truly has me stumped. I am teaching at an HPDE this weekend at Sebring, and it would be a shame if I had to leave my car at home. Anything that you guys could tell me would be appreciated...what am I missing here?https://rennlist.com/forums/graemlins/banghead.gif

Thanks in advance


Kevin

konakat

Check your fuel pressure. It could be your fuel pressure regulator.

kevinduffy

There is no fuel delivery, no spark and no tach bounce, as if it is a sensor issue.

J Berk

Does the 924s have a factory alarm?

kevinduffy

I am not sure if there is an option for an alarm in the 924S model, but this car does not have a factory alarm. I have had the car for eight years, with no real problems that stumped me like this has.

kevinduffy

UPDATE...Using a relay that I jumped, the fuel pump runs but it seems that the DME is not functioning. There is fuel with the jumped relay, but no spark and no tach bump.

I pulled the ground on the bell housing and cleaned all the contacts. No joy.

Anybody got a match and a can of gas?

cschmidt

Kevin,

In your posts, it said you don't see the tach bump at all trying to crank it? It should move a little - showing the sensors are being picked up. If not - the DME has no signal to trigger off of. Are you sure the new sensors are spaced correctly and the connectors up near the firewall are tight?

Good luck, just went through a no-start in January that turned out to be the DME.

Chuck

kevinduffy

Update...

Along the way, I decided to drop the fuse panels and relay panel and root around the wiring and see if there was anything obvious going on there. It also gave me a chance to check the ground under the dash way up high...all good. Nothing obvious, but in the process of doing this, the car will not longer crank. Turn the key, gauge and idiot lights come on, no crank. I tested the starter by bridging the starter terminals, and it cranks fine. Good battery, up to power since I have been charging it during this whole process. So the battery and connections are not an issue.

I then noticed that when I turn on the headlight switch, the headlights do not operate up and do not come on, but the rest of the lights do come on as normal. Hmmmm...

So the question is...what is the connection between the original no start, and now the no crank and no headlights? If I go by the Theory of Last Touched - the last thing that you touched is the reason for the problem now - then there is something in the fuse box/relay panel/wiring that is messed up.

There is something in the wiring so that when you turn the key to START, the headlights go out, and when you turn the car off, the headlights go off, leaving the rest of the lights on. I have been told that there is a "bridge" in the wiring under the dash that controls this function - it is not a relay, but a connector bridge. It shows up in the wiring diagrams, but I don't know what it looks like.

If there is something knackered in this "bridge," it could be the component that is causing me these headaches. However, the term "bridge" isn't the proper name for it, and in searching wiring diagrams and online parts diagrams (Automobile Atlanta), I cannot find anything.

While under the dash, I did clean up a couple of nasty wiring issues, but for the most part I just rooted around a bit. I have gone back through the tests with multiple DME's and such, with no luck at all.

So I have replaced the ignition switch with new, the reference sensors with new, the wiring harness from the reference sensors to the DME with new, coil with new, DME relay with new, as well as bridging an old DME sensor as per Clark's, new fuses, etc. The DME relay clicks when you turn the key.

So, any ideas? I have a really nice 924S M030 that is about to become a $250 parts car...

Thanks

Kevin

mel_t_vin

How old is the battery? What is the voltage across the terminals at rest?

Have you put 12v directly to the starter since your no crank issue?

kevinduffy

The battery is new, and I have been keeping a trickle charger on it during this process. When I put 12V to the starter, it operates normally.

I am leaning towards a problem with the device that turns off the headlights when going to START mode, but I cannot determine what that part is. It is not a relay, and although the factory wiring diagram points to a "bridge," I don't know what it looks like, so finding it has been problematic.

I have owned a dozen or more of these cars in the last twenty-five years, starting with a 78 924. I have built and raced four of them. This one has been in my possession for eight years, longer than any of them. I have been able to fix anything that has happened, but this time I am stumped. I am sure that it is something simple, but...

TurboAngel

Ignition switch would be my guess?

konakat

Yup, ignition switch. The lights work the way they do because the acc position works but the on position does not.

kevinduffy

The ignition switch was new last year, so I replaced it with a new one. No change. Then I took it apart again and plugged in another new one. No change. I have to assume the ignition switch is not the issue.

Thanks...keep thinking!!!

mel_t_vin

Kevin, re: your lights...there's a relay mounted to the headlight motor, behind the passenger h/l assembly. Have you tried to replace/swap out that relay [~$50] with a spare, or one from a functioning vehicle?

Re: your no-start...have you tried to replace/swap out your DME with a spare, or one from a running vehicle?

V2Rocket

Take a close look at the DME wire harness...broken wires?

there are plenty of sharp brackets and things to rub on/catch on under the dash...I had 18 wires short and burn up on the freeway a few years ago because of the bracket next to the steering column.