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[MikeDanger]

well luckily the 80 931 (semi parts car) had a new starter so I pulled that and put it in this car.

So after all this saga, heres how it ran, See what you guys think.


When I first cranked it, it would fire a couple times then die.
So i went and played with the mixture and got it to start, but barely, richened the mixture a bit and got it to idle for a little bit, but then once it started to warm up the idle started to drop.
So I then continued to play with the mixture quite a bit and the Idle screw. I finally got it to a point I though was good, let it run for a bit, Then shut if off. I let it sit for 3-4 min, then went to start it again...
It wouldn't fire... Ok so I play with the mixture some more and it fires up.. but when i would rev it it would not go past 3k or so and mis, Finally after more playing with the mixture it seemed ok. I shut if off waited about a minute and was able to start it again.

But what I dont get is, the last time i had it running, 3 days ago, it seemed fine, Why did I have to mess with the mixture?? I dont think I should have to adjust the mixture all the time.

Also one difference I noticed was that the previous time I had it running, it would rev extremely quickly, too much I though. Now, Not quite so quick. What does that mean?

another thing I noticed this time, as opposed to last time, was that whenI would rev it this time, There would be a puff of smoke comming from the exhuast manifold area (didnt a get close look) But I didnt realy pay attention to that, after the second start after I tweaked the mixture some more.



Lastly before I started the car last time, I took a look at the Distributor cap and noticed there had been some arcing in the contacts and in the plastic around the contacts. But the contacts themselves didnt look too bad. Would replacing it make any kind of noticeable difference? and will the one In my 80 fit?
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It was either this or a giant box of legos

[MikeDanger]

anyone put their 2 cents in?
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It was either this or a giant box of legos

[jason c]

A weak ignition system or improperly adjusted fuel system will definitely make it sluggish.
I don't know the whole story of what you've done to your car.....
The first thing you need to think about when the car runs, you work on it then it doesn't run is; what did I do?
When removing the air flow meter/ fuel distributor assembly you could:
1) bump it and knock the adjustment out
2) leave the intake boot loose or rip it causing a vacuum leak which will cause you to have to turn the cis up to compensate.
You should not have any leaks on the exhaust or intake side!
Recheck your work.
Make sure there are no leaks
Check and/or Adjust your cis pressures
Check the wires,cap,rotor & plugs.
Are the plugs fouled? Have they been fouled(Fouled plugs never seem to work right no matter how you clean them)?
Check ignition timing

[morghen]

You need to know the advance, the AFR and the fuel pressures.
Get the tools, test and rebuild necessary parts. Bring everything to spec and it will work.
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Supercharger and EFI kits
https://www.the924.com

[ideola]

How many times do we have to advise you to conduct proper CIS tests? You should NOT be playing with the mixture all the time. Follow the instructions in the CIS test procedure that we linked to earlier to make sure that system hot, system cold, control hot, control cold, and residual pressures are all within spec. Follow the procedure for verifying proper fuel flow and spray from the 4 injectors. It is pointless to do anything else until you do those six things.

If any of those six things are not within factory spec, you have more repairs to do on the basic CIS system.

IF all of those check out THEN use your WIDE BAND AFR to tune the final mixture. Once the car is fully warmed up (both coolant and oil temp to running spec), THEN let the car settle down to proper idle (950 RPM) and adjust the mixture until you are dead nuts on 14.7:1. DONE.
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erstwhile owner of just about every 924 variant ever made

[MikeDanger]

Ok did an actual test this time.
So here it is
ambient temp: 35F*
Cold Primary: 70psi (fuel pump jumpered)
Cold control: 73psi
Engine start: 60psi
engine running for 5min: 63psi

Now with the engine running I closed the valve for a moment, pressure went up to 100.


the car actually runs pretty decent But having the hot start issue now.

So I let the car warm up.

When i shut the car off pressure immediately drops to 30 psi. about 60sec later down to 20, then in less tha 5 mins down to 0. (And pressure drops with the test valve closed as well)

Now I started the car again a few minutes later and it started after a couple of cranks, and the idle was was low. then after about 2 minutes the idle went up to normal.
the initail pressure on start was 53 raising up to 55 later.


Shut if off and pressure dropped just the same, and then it was hard to start..

So its obviously not holding pressure and im assuming its the reason for the hard warm start. Now I know the injectors are not leaking. So Im assuming either the Pressure valve or the fuelpump check valve. (fuel pump is new, replaced by the guy I bought the car from( guy who bought it but didnt have time to fix it)
I had previously pulled out the pressure valve to make sure it wasnt stuck. Maybe I screwed up the seal. but I did spray some DW-40 on it before I put it back.
Can anyone tell me what the oring size is?
If that doesnt work Ill try a new check valve.


(and all that being said that was with the original WUR which I rebuilt. seems to run ok with it now.)

was too cold to continue since snow was mowing in.
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It was either this or a giant box of legos

[kcoyle]

These are the pressures for a 1980 931, I'd think they should be the same for an s2, not positive though. Can;t find that page at the moment.




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1982 931- Stock with MBC at 8psi

Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it.

[Ian89C4]

perhaps your fuel pressure accumulator does not work...per haynes manual that is what maintains your residual pressure after shut down.
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Ian Edgerly
North Carolina

Current:
1981 924 SCCA/ChampCar Weissach Race Car ("Serenity")
1987 924S ChampCar Endurance Car ("Der Weg")
1980 924 Euro ("Wahala")

[MikeDanger]

looks like it doesn have a check valve so ill start with that first.

It started right up today, idled well so I actually took it out on the road for for the first time for a couple miles, not too bad. probably should bleed the clutch and brakes, oil change etc and start stripping it down for weight
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It was either this or a giant box of legos

[emoore924]

Just to clarify for posterity, I think the check valve and accumulator are two different things. The accumulator(s) - sometimes there are two, live in the rear of the car mounted by the RR wheel well. They look like one or two very short beer cans with fuel lines. Not sure about what you're calling the check valve but I'd imagine it lives in the fuel pump body itself.

The accumulators leak externally, or they don't hold pressure internally and their failure is often the cause of hot start problems.

[morghen]

I'm not 100% sure on the specifics of the fuel acumulator BUT:

If the fuel acumulator would hold the pressure by itself the cars would have not been equipped with a one way valve just after the fuel pump.

So i guess that the fuel acumulator holds a certain amount of pressure by itself (probably low pressure just to keep the fuel system full of gas and not elt it fill with air).
All this while the real pressure holding is done by the one way valve that is mounted right on the output port of the fuel pump.
_________________
Supercharger and EFI kits
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