Mark Stahl

Hi, everyone-- I'm a bit stumped and could use some help.

My 86 5-speed had been running well for some time, until a few weeks ago when it would occasionally shut off without warning, usually at freeway speeds. It would act much like the ignition was cut off, for just a second or two-- than catch again. Happened maybe 3-4 times over about a month.

Then one AM, drove a short distance, got back in about 2hrs later- no start. Came back about 8hrs later ready to work on it--- started and ran great. Two days later, shut off while driving, wouldn't restart for a good long time. Eventually got it going on the side of the road by letting it roll downhill with the clutch out and eventually it caught. This time it ran poorly, just enough to get me home. Hasn't started since.

I swapped out all of the relays and fuses (this was something I'd planned to do anyway, bit overdue)-- nothing. Jumpered all of the important ones-- nothing. Changed out the fuel filter (it needed it anyway)-- but had fuel at the rail (didn't check the pressure but there was quite a lot of it when I checked.) There is spark at both coils and I pulled one plug on each side. Haven't checked the injectors themselves.

Did notice one interesting thing-- the tach is not moving at all when it's cranking. Does that mean anything? Could it be the crank position/ignition sensor? Computer? The alarm??

Any advice on next steps?

Thanks,
mark

Mrmerlin

clean the hot post and the 14 pin connector above it also inspect all of the fuses for corrosion clen these with a pink eraser as well as all of the other elex contacts.
A plug wire pulled out with an extra plug installed and a helper to crank it over while you look for spark usually confirms the CPS is good

PorKen

Probably the CPS. You'll probably find that the connector under the airbox has disintegrated.

Could be as simple as the EZF ignition brain connector not seated properly, too.

If you have to change the CPS, might as well put in some new 7mm ID return hose, WYAIT. Heck, put in a '87 S4 FPR, too.

Mark Stahl

Love the FPR idea

There is spark at the coils, and i pulled one plug (lazy?) and have spark there....

the CPS is under the airbox, right?

Will definitely reseat my brain connectors too

Mike Frye

As soon as you said the tach wasn't showing anything I thought CPS as well. I haven't replaced mine but I did loosen it and lift it up when I was working on the clutch (WSM says to do this even though I don't think it was actually required). Hopefully you can get it to come out in one piece.

I think there's a WSM procedure for checking the signal, but it requires an O-scope. I'd just remove the airbox and have a look, you'll probably find that the wires are frayed or the connector is so gunked up that you can't find the bolt that holds it in. I'd probably just order one and replace it just so I know it's new (that's what I've done with most of the things that are in or near the areas I've been working).

Mark Stahl

Thanks for the suggestions so far--

One question: does the presence of spark at a plug or at the coils mean the CPS is OK? One guess is that the injectors aren't firing (going to go in with a stethoscope when I can) -- would a bad CPS cause that?

Of course, I'm sure the CPS needs replacing anyway, but it seems I have spark and I'm fairly sure I have fuel pressure. What I'm not sure of is whether I have injectors opening. And of course the 'no tach' thing. It doesn't even spit like it's trying to catch... nothing.

-mark

PorKen

There could be spark, but the CPS signal may not be strong enough to indicate enough rpms for the LH to turn on the fuel pump relay.

Lizard928

My vote on the symptoms is for the CPS or reference sensor, or speed sensor are its other names.

Good luck with it. Coat the new one with silver never sieze so that it would be as much of a bear to get the origonal out.

Mrmerlin

another thing to check is the timing marks, turn the crank to TDC and verify that all of the marks line up,

borland

CPS on these cars provides two signals, (1) speed signal and (2) reference mark of crank position. The engine won't run without both signals, but may run poorly if its signal is impaired by a poor electrical contacts or dirt between the sensor and toothed ring gear on the flywheel.

John Speake

If you check out the CPS and find it OK, then the problem may well be the EZ-F ECU. They can give a sprak, but at the wrong time because they can't synch to the CPS.

Check your spark again, you may find it is not regular with engine speed, this indicates EZ-F failure.

Check the usual relays also .....

Mark Stahl

Well, changed out the CPS and still no joy. There is, however, some other sensor behind the CPS that's connected to nothing... can't find the other end. Anyone know what that is?

Anyway, at this point I've also changed out all the relays (and jumpered them all for testing) and cleaned the underhood multipin connector a the jumpstart positive connection (the plastic is ratty but all the pins fit nicely.) Am I left with an EZ-F failure?

-mark

dr bob

Mark,

Check circuit 15 with a test light/telltale and see if it's dropping out as part of your no start. That 15 drop-out would indicate a problem with the ignition switch. Clean ALL the battery terminals too, especially those little red wires on the positive that power the fuel pump and the injectors.

James-man

^^^

I'll side with dr bobs prognosis.

You can get a turn-key-and-no-nothing from simply a sticky relay (or more likely, poor relay contacts). I have lifted my passenger footboard about 1/2 dozen times over the last 7 years and after 3 or four gentle relay taps the car was brought back to life and for quite a long while. I love easy solutions and have been blessed with quite a few.

I have heard recommendations of carrying spare relays (or know which ones can swap out) just in case.

Mark Stahl

Cleaned the battery terminals.... no difference. How do I tap into circuit 15? The ignition switch is an interesting idea. I have also not checked into the alarm.

BTW, there was no change in my tach not moving when I swapped in the new CPS. Bummer.

I am this close to swapping out the computers and/or taking apart the rat's nest that is the fuse/relay board (I haven't looked at the back of it yet.)