3.2 engine trouble

[chrisf]

Please note, I have been doing quite a bit of searching last night in hopes of finding a plan forward to my issue. I’ve got several things I am going to try as I begin to trouble shoot. But I thought I’d post to see if anybody has any additional information.

My car is a ’76 RSR backdate with a 3.2l from an ’86. Yesterday I was out for a drive, and while sitting at a stop, the car died. I tried to start it; it would turn over but wouldn’t fire up. I was able to coast downhill to a parking lot. Let the car sit for a few minutes and tried again: the car started normally, ran for about 3-5 seconds then just died, like I had turned the key off. I had just filled up about 5 miles prior to that and was thinking it might be bad gas. I tried a few minutes later, and the car started and ran fine. I pulled onto the road and drove about a hundred yards, going about 35mph, and the engine just died (like before) but came back to life a few seconds later, so I continued down the road. Another 10 miles down the road, and it happened again. This time I was running about 50mph, but I noticed the tach went from about 3500rpm to zero as the engine cut out. A second or so later, it came back to life (tach was back on) and then a few seconds after that, died. I coasted to the side of the road and waited a few minutes. It started again, but only ran for a few seconds like before. Did this several times, and could actually rev the engine up, but it always died with a few seconds. Tach cuts out. I began the roadside trouble shooting:

1. replaced DME relay. No change.
2. jumped the fuel pump. It runs. I can hear fuel at the engine. Does not affect starting or running.
3. check all fuses and connections. Everything seems good.
4. speed and reference sensors are new, and car has been running great until yesterday. Everything connected at engine as it should be.

As I tried to trouble shoot, the car was less willing to start. Eventually it wouldn’t even fire, and had to have it brought home, where I’ll begin working on it tonight.

My plan is to check the ignition switch, check the speed and reference sensors, and check to see if I have power to the coil. I’ll also check for the two clicks I am supposed to hear from the DME relay.

I am thinking the problem is electrical/with the ignition system, b/c of the tach cutting out as the engine dies. It doesn’t sputter or cough or anything like that; It just dies like I had turned the key off.

Does anybody have any additional input? Is there something I may have missed or be over looking?

~Chris

[tharbert]

Check your grounds.

[chrisf]

Originally Posted by tharbert

Check your grounds.

forgot to mention that. I have checked the ground up front (by battery), the ones on the engine, and the one at the front of the transmission.

~Chris

[rick-l]

Originally Posted by chrisf

I noticed the tach went from about 3500rpm to zero as the engine cut out. A second or so later, it came back to life (tach was back on)

This means your DME is losing power or there is something wrong with the DME.

Is Ingo around?

Edit: I guess it could also be intermittent sensors (kinda rare).

[ischmitz]

Chris,

I think your diagnostics approach is spot-on. The fact that the tachometer cuts out pretty much implies the DME looses power or input from the speed sensor.

I agree with Rick that power would be my first guess and speed sensor my next guess. Then it's on to the DME itself.

Power is GND (you checked) and +12V from the DME relay (you already replaced) and the DME relay gets it's signal for the first stage from the ignition switch (when in RUN and START position)

While the car refuses to start, turn the key to RUN and listen to the first "click" of the DME relay and verify the ICV is vibrating. That confirms the DME sees power.

Good luck and let us know what you find,
Ingo

[chrisf]

man, you guys are spot on!

went home for lunch:

1. checked battery: just over 12v
2. checked coil with ignition on: about 12v (getting power)
3. key positions: no click from relay and no ICV activity, possible no-power to DME system condition.

so...back up front to the fuse panel to inspect my leads from key position/ignition on to the DME. I have three leads coming out of the bottom fuse terminal, kind off cramped. I pinched the lead for the DME and wiggled lighty. The wire pulled right out of the small cylinder crimp I had put on! I stipped it, and then clipped it to the little tang coming off the terminal block:

1. DME click
2. ICV hum.
3. immdediate ignition and instant idle, like nothing ever happened!

leason learned: that spare DME we carry should really be kitted with stuff like fuses, a couple of aligator clamp leads, wire pliers, small strip of sand paper, etc.....

here is a good pic taken a few minutes before this crimp failed. Let me just say that this is turning out to be one happy little car too!

[DRACO A5OG]

Outstanding! Congrats and She is a Beauty

So which number fuse was it? Yeah, I try to check all the the leads when I get a chance, couple of times found wire vibrated loose. Almost 300K on the clock will certainly jog something loose :-/

[chrisf]

this is turning out to be a nightmare. I tested the switched power supply to the DME last week, and that turned out to be the problem. I remade this connection last night, and now I'm having crazy problems. Fuse #18 (trunk lights, clock, interior lights) keeps blowing. Found a loose ground post under dash/behind instruments! tighten it up. Still blowing the 18fuse. Checked the battery to chassis ground again. Check the motor grounds again.

When holding the DME relay and turning the switch, I most times feel the DME relay turn on. Sometimes, I can feel the second click as the flywheel turns. Other times I cannot! Engine will start sometimes, but dies quickly.

not having fun right now. I'll keep everybody updated.

[chrisf]

stepped away for a little while, and then went back at it. Even thou I had checked the transmission strap, I felt that I was loosing a ground back there; I was loosing my DME ground. I ran a jumper from the two DME harness ground eyelets (attached to intake manifold) directly to the battery (-) terminal. All symptoms were gone! I ran the engine for about 5 minutes, and it was great. I pulled the jumper from the battery and it died. Would not start again. I reconnected the jumper, and viola: perfect.

now, for the fuse 18, I disconnected the hood lights, clock ( I thought it might be this) and replaced the fuse. glove box and interior lights are good. I connected the clock and all is good. When I got to the hood lights, it blew again. So I think my problem is there.

My plan is to tried to clean the ground at the intake manifold. If that doesn't work, I think I will just jump form there to a good chassis ground back at the engine.

[cary]

I'd spend some time on the transmission ground strap. That is your primary ground for the engine and transmission.

[chrisf]

I pretty sure about that strap. I've checked twice. The second time removing and sanding all surfaces. I think the problem is the powder coating on the intake, and the ground for the 3.2 wiring harness there. I start by filing that surface clean. If that doesn't get it, I'll just jump from there to the chassis, maybe from there down to the ground strap.

Thanks Cary.

[cary]

No, your dead on. Just get it back to bare metal.
Did you polish up all the ground loops too? Make sure you stack them so they all stack tight. There's a certain one that should be on the bottom of the pile.

Just had me engine out 6 or 7 times working on a new lightweight clutch and flywheel package.

[RedCoupe]

Chrisf, I would also check the resistance of the ground straps and not just rely on a visual. There can be internal corrosion between connector and wire that you cannot see. I had a similar stalling situation with my 964 and after much searching it was just the main ground strap from the battery.

[chrisf]

I put a temporary jumper under the wiring harness ground on the intake over to the rear chassis ground behind the coil/driver's side. Drive for about 15minutes and the car runs great. It actually seems smoother and a little quicker!

Seems like it was the wiring harness ground on the intake manifold.

strange that I had a number of issues that all came up at once.

Thanks for all the input.

~chris