No Warm Start

[cajun]

Well, getting ready for track season and the universe is making me work for it.

My '81 SC 3.0 starts and runs like a rock star... Problem is that after it warms up and I shut it off it will not re-start.

Here's the part that has me scratching my head. If I let the car sit for 15 minutes, It will start and run again just fine.

Not sure where to begin, but I am convinced the issue is something minor.

Please someone throw me a life line!

M

[ossiblue]

Start with a pressure test for residual pressure. If your residual pressure does not hold, you will not have fuel in the system for a restart and the cold start valve will be inoperative due to the thermo time switch. If your residual pressure proves to be bad, the most like culprits, in order, are: fuel pump check valve, fuel accumulator, wur, fuel distributor pressure relief valve. Each can be tested to find which is at fault.

Simple test. When the no start occurs, remove the air cleaner, gently lift the plunger inside the intake (ignition key "on"), listen for the fuel pump running and the squeal of the injectors (do this only for 2-3 seconds.) If the car now starts, it's likely residual pressure.

[jeffs9146]

Fuel Accumulator!

You can test it by turning on the key and pushing up on the AFR plate in the airbox and try to start it! Pushing up on the AFR plate primes the pressure!

I had exactly the same problem and I replaced the Accumulator, problem solved!

[cajun]

Gentlemen,

THANK YOU. A good friend of mine who rebuilds these motors (he rebuilt this one) offered a similar diagnosis.

THANK YOU THANK YOU THANK YOU.

I will keep you both posted.

[Bob Kontak]

Originally Posted by jeffs9146

Fuel Accumulator!

You can test it by turning on the key and pushing up on the AFR plate in the airbox and try to start it! Pushing up on the AFR plate primes the pressure!

I had exactly the same problem and I replaced the Accumulator, problem solved!

Accumulator is a common residual pressure loss contributor. However, it's $203 and is not the only place you can lose residual pressure. Just saying. Need to isolate.

[cajun]

Followed Ossiblue's advice and still no start. Wait 5 minutes and she kicks right off...

I dunno...

[timmy2]

Try swapping out the red fuel pump relay with the horn relay when it does this.
Also try spreading the pins on the red relay with a razor blade. May be getting hot due to poor connection and pump doesn't run until it cools off.
Only saying this due to failure of lifting the plunger to get it to start. Did you hear the fuel pump run when lifting?


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[ossiblue]

Originally Posted by timmy2

Try swapping out the red fuel pump relay with the horn relay when it does this.
Also try spreading the pins on the red relay with a razor blade. May be getting hot due to poor connection and pump doesn't run until it cools off.
Only saying this due to failure of lifting the plunger to get it to start. Did you hear the fuel pump run when lifting?


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+1 on Timmy2's advice. Be sure the fuel pump is running and that you hear/feel the vibration of the injectors. If the pump is running during the test and the injectors are, in fact, shooting fuel, the only other reason for a no-start would be ignition.

Please let us know about the fuel pump running and injector squeal.

[bxtech]

What happens when it's warm and you try starting it with the accelerator pedal pressed halfway down?

[Joe Bob]

BTDT, check valve in the fuel pump neck. used to be a 20 dollar part....

[Bob Kontak]

Originally Posted by bxtech

What happens when it's warm and you try starting it with the accelerator pedal pressed halfway down?

All you are doing is adding a little air to the mix. If you have a rich condition - not running rich, just rich at warm start, for whatever reason, it will help.

The 911 will start cold on hot first turn of the key if working right.

[Joe Bob]

Boboboboboboobob.....CIS is fuel pressure. The only way that pendejo will start is with ether, trust me.....BTDT.

Smoke another bowl or buy a part from Lonewolf.......jerkoof wanker douche nozzle.....

Love and kisses. %^)

[boyt911sc]

Originally Posted by cajun

Well, getting ready for track season and the universe is making me work for it.

My '81 SC 3.0 starts and runs like a rock star... Problem is that after it warms up and I shut it off it will not re-start.

Here's the part that has me scratching my head. If I let the car sit for 15 minutes, It will start and run again just fine.

Not sure where to begin, but I am convinced the issue is something minor.

Please someone throw me a life line!

M

M,

Do you still have CIS in your '83? We need to know your control fuel pressures cold and warm including residual pressure. When the engine fails to start after warming up check the resistance reading (Ohms) and presence of ignition spark. Please post your findings. BTW, do you have Permatune or Bosch CDI?

Tony

[ossiblue]

After rereading this thread, I'm leaning toward an ignition problem. The warm start problem is typically associated with a residual pressure loss but in your case, it starts when more time passes and that doesn't make sense as residual pressure will not increase over time. Additionally, your test using the plunger did not alleviate the problem. Tony's question about the CDI is worth an answer as well.

Just throwing it out there because I have no experience with later CIS, but can a faulty frequency valve or electrical connection related to it cause a problem like this?

[Bob Kontak]

Originally Posted by Joe Bob

Boboboboboboobob.....CIS is fuel pressure. The only way that pendejo will start is with ether, trust me.....BTDT.

Smoke another bowl or buy a part from Lonewolf.......jerkoof wanker douche nozzle.....

Love and kisses. %^)

Great to hear from your ass-clown self and thanks for the kind words, my friend.

I just answered the question of bxtech regarding if the "gas" pedal is halfway down. The gas pedal had nothing to do with gas or fuel pressure and all to do with air.

I have planted the pedal on my 911 to air the intake out on hot / humid days in Houston while cranking. Helped as it finally started. Anomalous situation, though.

[Bob Kontak]

Originally Posted by boyt911sc

When the engine fails to start after warming up check the resistance reading (Ohms) and presence of ignition spark.

Tony, what resistance reading are you speaking of? The warm up regulator or the coil pack in the distributor?

I think your recommended secondary spark test is the first I would perform. If no spark then we can dig in.

Need input on if P-Tune box, although both of my legacy P-Tune boxes would die while operating then take 5-15 minutes to restart.

[porsche930dude]

id also say fuel accumulator or fp check valve. good time to change the hose from the tank aswell. mine looked like it it original and about to snap right off. This is a common problem and no reason to investigate other things unless they are properly checked or replaced

[boyt911sc]

Originally Posted by Bob Kontak

Tony, what resistance reading are you speaking of? The warm up regulator or the coil pack in the distributor?

I think your recommended secondary spark test is the first I would perform. If no spark then we can dig in.

Need input on if P-Tune box, although both of my legacy P-Tune boxes would die while operating then take 5-15 minutes to restart.

Bob,

I was referring to the WUR-090 that is supposed to be in Cajun's engine (?). Unlike most 0-438-140-xxx type Bosch WUR's, this particular WUR has a thermal switch for cold resistance and warm resistance readings. I was curious to know the resistance reading during a cold start.

Tony

[Bob Kontak]

Originally Posted by boyt911sc

Bob,

I was referring to the WUR-090 that is supposed to be in Cajun's engine (?).

Thanks Tony.

I think your spark test is the easiest in the short term to determine the direction of analysis.

[targa80]

The warm start problem is the loss of fuel pressure in the lines as previously stated by others and the fuel pump has an internal check valve that can fail which allows the fuel line to drain back into the tank. I had this problem many years ago and I did pressure testing of the fuel system. My diagnosis led me to the Fuel pump internal check valve failing, bought the external check valve and fixed the problem (cheap fix). If you decide this is your problem and you buy the external valve make sure you also buy the added hardware to adapt to the original banjo fuel line fitting.