Porsche 930 Project won’t start

[TrickyDSE23]

Hi guys,

After a few years away I have finally taken the plunge and jumped back into Porsche ownership, found a lovely 1985 Porsche 930 without an engine and shipped it from Florida back to the UK to mate to the low mileage 930 engine from the same year that i’ve had In storage for about 10 years now.

The car has arrived, i’ve got the engine in and all plumbed in, drained the old fuel, changed the oil, changed the filters, changed the plugs, replaced the front fuel pump which seemed to do nothing, then turned the key thinking it would just start, but no such luck.

When I turn the key the engine turns over happily and sounds like it is trying to fire once, but it doesn’t run on from there, sometimes when turning it over there will be a small backfire.

I’ve done a lot of reading about this and checked the following:

Thermo Switch: working

Fuel Pumps: definitely running

Cold Start Valve: Removed, powered up, definitely works, atomises fuel

Drained all fuel up to injectors, new clean fuel in the system

Fuel is definitely getting to the Cylinders

Warm Up Regulator: fuel passes through, I am assuming this means that it works correctly or well enough for it to run I would think

Auxiliary Air Valve: open at start up

CDI box whines with ignition on, tested as per post I found on Pelican Parts, all terminals give readings as they should, however when I test the power going from the CIS box to the coil at the white cable terminal I get no reading at all for AC voltage when the engine is cranked, however I have checked the spark plugs and I am definitely getting a spark (possibly dodgy multimeter, but never had an issue previously)

I don’t seem to have any vacuum leaks

If anyone has any ideas about what I could test or what could be wrong that would be amazingly helpful.

This morning i’m going to test the timing with a strobe tester, after that i’m going to pull out the engine and compression test the cylinders, I did this a couple of years ago and it was all fine but i’m going to re-test because I’m starting to run out of ideas.

I can’t understand how with fuel and a spark being delivered into the cylinders that the engine won’t run, even if it sounded like an utter dog

Many thanks for any responses or thoughts.

Rich

[Bucketlist]

Did you read through the above thread "Common answers to why My car doesn't start or it's running poorly...."?
You don't mention checking fuel control pressures with CIS gauges, many threads on this.
I would want to know these numbers plus fuel flow and injector flow.
A backfire from the intake usually means lean fuel mixture and from exhaust means rich.
Good Luck!

[mark houghton]

Does the air flow/fuel metering arm move freely? If not, it won't open up the ports in the fuel distributor enough to flow fuel to the injectors when cranking the engine. Pull off the plug for the metering arm switch, thus allowing the pumps to run continuously with just the key turned on, then depress the metering arm with your finger (push down firmly on the mixture adjusting post if the air cleaner hasn't been removed for access to the arm plate). You should be able to hear the injectors squeal. That should dump gas into all cylinders and you should be able to fire up directly after that maneuver for at least a second or so.

You've got spark, but is the timing correct? Maybe also look at the green distributor wire that carries the signal to the CDI. Lastly, although you do have spark, perhaps it's very weak which might indicate a bad coil.

Just throwing out ideas here....

[jadewombat]

If it hasn't run in a while the compression in cylinders won't be that good until the oil pressures up.

Try and spray some starting fluid in the intake. If the car starts and runs a few seconds then you have decent spark and should help reseat the piston rings.

From there you can check and make sure the fuel meter is working as Mark suggested. CIS injectors won't pop open until 40 psi is reached or the meter arm is raised a certain portion.

[T77911S]

check the plugs to see of they are soaked with fuel.

verify spark plug wiring is correct
backfire could mean the wiring is wrong.

[TrickyDSE23]

Hi guys, thanks for all of the replies, after checking the compression which seems good, and adjusting the ignition timing I think I have narrowed the issue down to the fuel system.

I was able to get the engine to run for a few minutes by manually depressing the control pressure plate, although the engine wouldn’t tick over on its own. However when it was running the control pressure plate wasn’t affected by the position of the throttle which seems a little strange

I don’t have a CIS pressure testing kit, so i’m unable to test the pressures until probably next week at the earliest

[RarlyL8]

Could be that the fuel distributor piston is hanging up in the bore. The engine runs cold so fuel is able to circulate. The problem may cure itself with fresh fuel bathing the piston. If not I would remove the fuel distributor and see if the piston moves freely.

[TrickyDSE23]

Thanks for the idea Rarly, I tried to pull the Fuel Distributor off earlier today but after I had disconnected all of the lines and taken the holding down screws off I couldn’t pride it off, is it held down by any fixings from underneath perhaps?

[flightlead404]

Originally Posted by TrickyDSE23

I can’t understand how with fuel and a spark being delivered into the cylinders that the engine won’t run, even if it sounded like an utter dog

fuel and spark (or at least spark with a cis system) needs to be delivered at the right TIME.

Do you have the dizzy in 360 deg out of timing?

[flightlead404]

Originally Posted by TrickyDSE23

Thanks for the idea Rarly, I tried to pull the Fuel Distributor off earlier today but after I had disconnected all of the lines and taken the holding down screws off I couldn’t pride it off, is it held down by any fixings from underneath perhaps?

The fuel distributor is held on with 3x13mm nuts front, back, and right as I recall.

that and the fuel lines of course including to the csv behind it, and the connector for the airflow plate contact

ref your previous message the airflow plate is not controlled directly by the throttle, its drawn down by the passage of air, which is in turn controlled by the throttle. moving the throttle will have no effect on the airflow plate unless the intake is all together and the engine is running.

[RarlyL8]

There are 3 flat head screw bolts holding down the fuel distributor from the top. If these are the hold down screws that you removed then the FD is stuck on the o-ring which is pretty common with age. Gently pry around the bottom with a flat blade screw driver and it should begin to move for you.

[jadewombat]

The piston in the middle of the fuel distributor is a metal to metal fit. Very, very susceptible to scratching so I wouldn't remove it to clean it.

You can take the whole fuel meter off with the lines disconnected, turn it upside down and spray some cleaner around the base of the piston to free it up.

Once it frees up you should be able to see the piston following the meter arm.

[TrickyDSE23]

I was suspicious of the piston in the Fuel Distributor prior to installation, out of the car the pressure plate depressed with mild resistance but the piston seemed to take hours to return to the original position, I had talked myself into thinking that it was the fuel pressure that caused the piston to return. Perhaps I was incorrect

[T77911S]

if the piston is stuck, you will have free play in the sensor plate before it makes contact with the piston, if it is stuck in the up position. also the same if it wont drop back down.
so as soon as you touch the plate you should feel resistance

[TrickyDSE23]

Just a quick update, thanks everyone for the advice and suggestions.

I finally narrowed the problem down to a bad fuel accumulator which was letting fuel pass straight into the return line meaning the pressure was too low. Also the previous owner had totally screwed up both the idle adjustment and the adjustment for enrichment.

Just a few more little things to do and hopefully she’ll be on the road. Fingers crossed less than a week