924Board.org

[924RACR]

PS - this looks like the CIS pressure tester I have, has worked great for many years...
https://www.harborfreight.com/deluxe-fuel-injection-service-kit-58817.html
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Lakeview]

@Raize. I tried your recommended attempt on unhooking the air valve. With the pump jumped I let it run for at least 5 minutes. Fired a little better but still not run. Would fire consecutively. When I raise the flap and add fuel it won't do that. Takes a while to get back to firing. Holding the throttle wide open when it does fire it revs real high and dies. I have a small fuel leak at one of the mounting screws. I think the head is my problem. Searching for a replacement now. Looking at distributor heads people are advertising two different ones for 924. Mine ends in 005 but I also see one that ends in 039. Old Bosch part listing shows both. Not sure what the difference would be.

924RACR. Yep. Lack of information on a 1983 model.
Can't afford an EFI conversion. It's more than what I gave for the car! Plus, I like things original. I got a lot of documents with the car dating back to when it was sold new. I'll just keep fighting!

I have looked at the Harbor Freight one and it's in stock at my local store. Debating on it or just building one. The 924UK site shows how.

[Raize]

[Lakeview]

@Raize

Same here for not being on here.

I purchased a FD head from the UK at the first of the month and still waiting on it. Hopefully sometime between now and the towards the end of the month. It was described as coming from a running car. I tortured the seller and paid 55 pounds. I'm gonna bolt it on without cracking it open and see what happens.
Just been focusing on my 944 while patiently waiting.
I'll be back for an update when I get it installed....

[Raize]

Hopefully new metering head will fix it but you will still need to adjust the mixture screw to match the new head, they're not really plug-and-play.

Since you will have to adjust it anyway, why not try something with the existing head first like:

1. Unplug all 3 of the K-jet accessories (WUR, CSV, AAV)
2. Back off the screw by 5 turns
3. Try and start the car for 5 seconds
4. If it doesn't start, turn the screw in by 1/6 of a turn (easy to track wtih hex key)
5. Once you got back to your original position (e.g. 30 tries) then give up.

Going from lean to rich like that with the CSV disconnected will at least not cause flooding / wash the bores with petrol and you might actually get it to idle.

The normal advice is to adjust it until fuel is just welling at the meter head and then back it off a half turn but this is WAY WAY WAY too rich in my experience (to the point it won't start) and it's much better for your engine to experimentally go from lean to rich than rich to lean for reasons I said above.

[Lakeview]

@Raize

Thanks for the insight.

I just checked the tracking and it has hit Chattanooga, TN which is about 5 miles away from my Georgia location. Hopefully it will be delivered tomorrow.

I will try your suggestions first just to see if it makes a difference. I don't feel confident though. I have a very small amount of fuel seeping from one of the mounting screws holding the head to the housing. I'm thinking something internal is not right.

I hope to have a positive update soon!

[Lakeview]

@Raize

I received the FD head yesterday actually.

I installed it. Got it cranked. Idled around 900. Smelled rich and was kinda hard to start.

Started turning the mixture toward lean. Got it to the point it would restart regularly. Idle went up to about 1050 with the idle screw turned all the way in. Letting it run for 10-15 minutes. Ran great. It would restart immediately but if I let it sit for about 5 minutes it was very hard to get restarted. Once started it would idle and run fine. Idle up to about 1100 now though. No more rich smell.

Could the accumulator lose pressure that quickly? Or???

Unrelated but it was showing hot on the gauge. I added about a half gallon of coolant. PO had replaced the water pump and the fan is coming on normally. I'm thinking it may be the coolant temp switch. Gauge fluctuates from full hot and then cools back to about middle line. Does not force out any coolant with the cap on.

[Raize]

That’s good. Are you starting with full throttle applied? It says to do that in the owners manual for hot starts.

The 924 hot starting is just crap, even when everything is in working order. One of the biggest and most unavoidable problems is the system will follow the WUR pressure so you lose a lot of pressure instantly from that. Does yours have the hot starting solenoid system?

Coolant might need bled. The temp switch measures at the radiator but the temp sensor is at the back of the head so they’re not fully in sync.

[Lakeview]

Raize

It will crank right back up when turned off and immediately restarted without touching the pedal. Let it sit a few minutes and it will eventually crank holding the pedal down.

Not sure but are you referring to the small two wire solenoid with the fuel line running off the FD head? It has that.....

Yep, I thought about that and was more concerned with the running. I'm going to try and "burp" the coolant system next.

Does the temp sensor on the head run the gauge? Gauge can be very erratic. It can go from pegged hot and bounce back to the normal range very quickly. I know it's not as hot as the gauge says. With the cap on and the system supposedly pressurized it's not forcing coolant out.

[924RACR]

Sounds as if you should maybe check your wiring to your temp sender - yes, the one on the back of the head, for the gauge.

I would ask for some correction to your terminology; the terms you're using are misleading, as you're using them, and can REALLY create confusion as such.

Crank: engine is rotating by the starter only. Also sometimes turning over (again, vague and misleading because imprecise so not recommended)

Fire: ignition and combusion are happening - engine has started or is, if not firing on all cylinders, at least sputtering and attempting to start.

I would rewrite your statement to be:

[Lakeview]

924RACR

Let's see if I can simplify it for you....

If the car is running and running fine for any said amount of time. Turn off. The car will crank, refire and start back running normally. Off, back on with no wait time.

If I let the car sit for say five minutes it won't restart immediately. It has to be cranked on for a long period of time before it will start and run again. When started again runs normally. Idle, throttle, etc all seem normal.

Does this clarify it for what your question/comment was?

[Fifty50Plus]

Sounds like a bad check valve between the fuel pump and fuel distributor slowly bleeding off the internal fuel pressure.
_________________
1979 924 NA race car H-Prod SCCA
1982 924 NA race car - Sold
1981 924 Turbo sold
1982 924 Turbo sold
1972 911 E race car - traded for Cayenne Diesel
1975 914 1.8 Building for H-Prod SCCA