harveyf

I need some advice from the collective brain trust.

86.5 928. Recently purchased by me about 3 months ago. This is the car I bought from Joel Roberts. FYI I am pretty sure Joel had performed an intake refresh and cleaned the grounds.

It has performed fine up to the current situation. I drove it on the weekend and parked it in the garage, which is unheated. I came back about 5 days later and tried to start it. It cranks and sounds like it's trying to fire, as I get intermittent firing pulses but it will not catch and run. It seems similar to an engine with the timing retarded.

Tests so far:
1) Battery voltage measured low after cranking. I subbed in an alternate battery and an alternate ground cable. No change.
2) I put my inductive timing light on all 8 spark plug leads (one at a time of course). Every spark plug lead fires the timing light at what appears to be a reasonable pulse rate.
3) I put an aftermarket fuel gage on the end of the fuel rail. Reads about 40 psi.
4) I listened to the front 2 injectors (front injector on the left and right banks) with a stethoscope while cranking. Both "click" while cranking. I have not pulled any plugs yet to see if they are wet.
5) I tried spraying starting fluid into the air intakes. No change.
6) The tach certainly bounces. Actually it swings up to around the redline while cranking. This is much different from the behavior of my 944's but as I recall it was also doing this before the problem manifested itself.

So I think I have fuel and spark and have no reason to suspect compression (it was checked at the PPI and found to be fine) so that covers the 3 basics. Any suggestions on where to head next would be appreciated.

John Speake

Although you apparently have spark, I think it isn't correctly timed. The EZ-F has to synchronise to the CPS signal. Sometimes they can go faulty and not synch. The problems could be a bad CPS or it's connector under the engine air filter, or the EZ-F itself.

A swap of the 3 vital relays is a good idea before getting into deeper fault analysis. LH, EZ-F and fuel pump.

OTR18WHEELER

I cant offer any technical suggestions, but FWIW my 928 acts just as you described after sitting for a couple days in below 20 degree temps, it will cough a bit before it actually starts, and I have to hold the idle at around 2k for a half a minute to keep it running, but after that starts right up as long as the engine is warm. I ran the battery down once, but put the booster charger on it and it fired right up. In my case, I think I have a bad Idle controll valve.

GregBBRD

"So I think I have fuel and spark and have no reason to suspect compression (it was checked at the PPI and found to be fine) so that covers the 3 basics." Obviously, if this is true, the engine will run....so something has to be "lacking".

Although not very common, I've seen a few of these engines strip off a few teeth from the timing belt (just before removing them all).

If the cam timing is far enough off, the engine will not start/run.

I've also seen people get a load of fuel that has water in it. When the car sits, the water settles to the bottom and then is what the fuel pump has to work with. Drain off a bit of fuel from the fuel rail into a clear container and see if there is any water contamination.

The next step would be to pull a spark plug and see if there is anything strange on the plugs (like water.)

harveyf

Thanks for the suggestions so far. That gives me a few things to check this weekend. It really does feel like timing (either spark or cam) as it is trying to fire.

OTR18WHEELER

bump..just to add a side note, after my last post here, I added a can of sea foam to about a half tank of gas, drove a few hard miles and the car sat in the garage until yesterday (01-12-14), It fired right up, and never shuttered or died. I beleive the sea foam helped clean something.

chitown928s4

Make sure you didnt flood it. Pull wires out an inspect spark plugs. Did the samething last week tryin to start after the battery died from the cold. Cranked her too long ans somehow flooded her.

harveyf

An update: When this occurred I had just started a major "refresh" of the New Hill Garage with new epoxy floor paint. Everything was scattered into temporary storage locations to clear out the floor. Just like when you restore a car, the new floor paint made the walls and cabinets look shabby so they got painted next. Then I built a new metal covered workbench for welding work and a new melamine topped table for "clean" work like engine assembly and upholstery. I'm just now getting everything back into the shop. I only get home on the weekends.

In the interim I acquired a set of shop manuals. The 32 valve 86.5 seems to be a little bit of a bastard child as it has the dual coils, dual "distributor caps" on the ends of the cam covers, and dual ignition trigger units but does not seem to have the diagnostic capability of the 87 ECU. So I am struggling to learn the layout of the system in advance of doing further troubleshooting. I am steep on the learning curve right now. It is definitely not a flooding issue as has been allowed to sit a week between start attempts.

If there are "amendments" or updates for the shop manual that address specifically the 86.5 setup I would love someone to point out to me how to obtain them. My manual seems to jump straight from the previous setup with the dual distributors connected by a little drive belt to the full electronic version with the diagnostic readout capability.

My next goal is to check the timing of the cams and to figure out how to use my timing light to check baseline timing while it cranks, as the symptoms still point to it being a little bit off timing wise.

neilh

Harvey, PM'd you... I may have some manuals that could help....

SteveG

"Intermittent" is always fun. I would re-check all the grounds yourself, there are several that can affect ignition; often overlooked are the coil grounds; you may have spark, but a weak spark. What volts do you get at the 14 pin when cranking?

Landseer

Tach to redline is unusual behavior. I'd pull the air filter, clean the two critical grounds, and take a real hard look at the MAF connector and wire condition; same with CPS. Would probably replace the CPS.

I'd check the timing marks (86.5 can be checked via the hose vent holes), then pull both distrib caps and clean the contacts.

Battery needs to be fully charged.

Has petrol, right? Take a quick peak at the tank, too, to insure it hasn't imploded.

Dozens of things to check. Distib cap corrosion has been a problem for me on 85 and 86 cars during wide temp and humidity changes.

Hard to know where to point you without knowing maint condition of the car.

harveyf

Understand. Thanks to all who replied.

joejoe

harvey, I have been fighting a hot-no-start problem on one of my 86.5 for awhile. This car was a calif. gross pollutor and had not had any service in over 8 years. Underneath the top I found multiple vacuum leaks and frozen isv as well as 4 original spark plugs,original plug wires (car has 122k) driver side injectors replaced, crumbled tps wire, throttle rod bent, cracked/hardened vent hoses and the oil fill had been replaced with one from '87/later that was cracked and filled valley with oil.

Car has had all this replaced and I fought a failing MAF calibration until 4 days ago when replaced with rebuilt unit from 928intl. While I was able to get car to pass smog with bad MAF, (1 1/2 yr ago) this last trip to sharktoberfest seemed to finally kill it. Old MAF was checked and ohm was at 978. New unit is set 382 and has started both hot and cold with no problem. Today I will check with kens' blinkr' for co and idle (idle is close but maybe 800 rpm high)

Now I am not sure why, but this car will smoke the tires through both first and second and seems much crisper and quicker than my other 86.5.

Mrmerlin

FWIW starting the early 32 valve engines and not driving them or otherwise letting them get to temp seems to foul the plugs,
this condition is made worse with old ignition wires and worn intake parts ISV TPS harness and old MAF and leaking dampers and FPR and old temp 2 sensor , low battery starting voltage caused by dirty corroded connections

Make sure everything is as new as possible and that you drive it like you stole it

Harvey at this point I would pull the right and left cam tower covers and check the belt for the timing and belt condition, if good replace the plugs charge the battery clean the terminals connections and start the car and go for a drive

Bilal928S4

Check the tires, they might be hard or dry rotted compared to your 86.5 or near the end of their useful life.