SMTCapeCod

Interesting how these faults seem to run in little pandemics...I guess there are often enough folks suffering from them at any given time, that they seem to wash through the community at once.

I noted a slightly slow start on mine couple days ago. Then yesterday, three looong cranks to get it going. It wasn't missing, wasn't out of time or one side of the ignition- just freewheeling. Cranked but sounded like no spark. Then it started after I floored it, but that may have been incidental- caught immediately and ran smoothly. After parking during errand- two looong cranking sessions, then fired right up.
Last thing I did? Swapped in a refreshed ECU and I thought the tach needle was an indication of a fault there- but I didn't see that with mine. Yes I note S3 cars here.. I said aha and swapped back in the prior ECU..but the condition persisted.
Added to the list.

davek9

If opening up the throttle did in fact help it start, maybe a leaking fueling issue, did you smell any excess fuel?

Remember moving the throttle off the Idle position changes the ECU Map to cruse or WOT depending on how far you depress the go peddle

Dave

SMTCapeCod

Non detected. No poof of white smoke or spluhtter when it started either, just vrroom.

ramcram

I'm always suspicious of immobilisers, never trust them. I couldn't start this one, and in prep for going away for a while, I fully charged the battery, then disconnected it. On return a few weeks later, connected up the battery, recharged it and it fired up immediately. Aaaah, says I the 'jolly' immobiliser, next won't start I disconnected the battery and tried again, still no go.
Started 2 days in a row just now. Took it for an amazing fang through the hills and came back with a smile like a split in a water melon.
I bet the smile won't be there next start.
I just don't have time to trouble shoot right now.

ramcram

Just a quick update to this. I sent the 2 ECUs to John at JDS Porsche in England to have them both overhauled. He is also suspicious that the symptoms point to the EZ unit.
As the car has just had its 30th birthday, it deserves a refresh even if this is not the issue.

bureau13

FWIW, I had this same problem. Due to it being intermittent, you can never be quite sure when you fix it...I had it "fixed" twice, before I actually fixed it. The actual fix? The stupid wire to the positive battery terminal...not the big one, but the smaller one that runs the fuel pump...was loose and somewhat corroded, and giving me an intermittent fuel pump connection. Cleaned and tightened, it's never not started since. However, I didn't have the tach issue...that does sound a little CPS-related.

Does the '86 ROW actually have an in-tank fuel pump? The '86 USA cars do not...

John Speake

The tach behaving as described suggests the EZ-F is having problems synchronising to the CPS.

See if you can borrow a known good EZ-F (just plug it in, no need need to bolt it up) and see how that behaves.

Landseer

First, its never that bad of a thing to have MAF, brains, sensors replaced on a 30 year old car, ie throwing parts at it. Ends up being an investment of sorts.

I've had a similar situation/symptom happen on our 86.
Last time, wife was at a food store in hot july, car full of groceries.
Swapped a lot of stuff, maf brains,from our 85.
Limped home.
Cleaned the CPS connectors and all grounds and terminals with great care.
Nothing.
Changed CPS -- solved. CPS was only 5 years old.
Strong suggestion you buy one and change it.
As next step if you don't have an ocilliscope handy.

Side note, wife was very pissed-off, as the intermittent crap left her stranded 3 times in a 30 day span of time. (previous 5 years/30,000 miles were flawless).

That 928 now lives in a barn out back and a f;ng Hyundai coupe is in the garage. I drive the 86 most days myself and it has been dead-nuts reliable.

So CPS can fail intermittently in my empirical experience.

ramcram

Yes, the ROW does have an internal fuel pump and it was seized. The tank was drained and flushed, so the pump came out then. Fortunately I had a new spare in my shed.
I know the wires you refer to and they have already been checked when the battery box was cleaned and re-painted.

ramcram

I have a spare pair of ECUs but they have stock chips in them and this car is setup for the S300 chipset.
I'll just wait for the refreshed ones to come home. AusPost says they have just arrived in Cambridge.

ramcram

Another update. I've received my 2 engine control units back from John in Cambridge and they tested just fine. No problems.
I put them back in he car, turned the key and it stated up and ran fine. Drove around the block like it never had a problem.
Next day, won't start!
Pulled the Kick-down relay out today as part of the next step and it's the wrong one.
It's 928.618.109.01 and my model 86 ROW should be 928.618.109.00, which is no longer available but I had bought a s/h one from 928Intl, put that in and she's running again.
We'll see what she feels like tomorrow?

Snark Shark

Sounds so much like my ABS relay. Half the time it would start with no warning light. The other half, the relay would click erratically. Replaced the relay, and now it works perfectly. If the relays are new, maybe they're getting inadequate voltage due to corrosion somewhere.

ramcram

Well, it did start the next day! So, moved it out of the garage, left it idling while opening the gate, put the foot down to blast off and nothing, just died on the spot.
Ah, says I, the last thing touched was the kick-down rely and it started, so I wriggle that and away she went!
Now to pull out the CE board and see what is loose?
I think I may have found it.

ramcram

next update.
CE board removed, looked very good. Took out all fuses and relays, cleaned everything with Deoxit and tested various current tracks and it passed with flying colours.
Refitted all fuses and checked them. Refitted all relays with new ones for all 53 type. Put the board back and she fired up first time and ran beautifully.
Well that was Monday. Today, Friday put the key in and turned to hear the lovely even sound of the starter and nothing else! Not a hint of firing.
Thoughts of Basil Faulty, if only there was a tree branch around "I warned you, I'll thrash you within an inch of your life".
Oh the joys of intermittent faults.

gazfish

I had a similar problem, I suspected the dysfunctional alarm or immobiliser wasn't powering the LH relay. I connected an LED and resistor to the LH relay power pin and sure enough the next time it wouldn't start the light was going out when I cranked.
I bypassed whatever was dropping the voltage based on the wiring diagram and haven't had a problem since.