Cylinder #5 does not fire after hot restart

[Scott R]

Until this evening I thought I had lost #5 on my SC all together, however that's not the case. When #5 is started from cold it fires just fine, I can remove the injector plug and the RPMS drop, and I can do a thermal test and it's fine as well. However when I shut the motor down hot and leave it for about 15 min;s, I then try and restart it and my RPM's are low and #5 is dead. Any ideas on what I should check? It's not fuel becuase I have tried two injectors, and when the cylinder is down I get fuel ignition in the exhaust system, the compression is fine, hell it fires until I shut it down. I'm stumped!

[2.7RACER]

Scott,
You've got fuel and compression and no go bang.
What else is left?
If necessary switch primary wires to 5 & 6 at both ends.
Attach #5 wire to a plug outside of the motor and verify spark.
Check distributor cap. Double check firing order.
Make sure the wet plug is dry.

[Scott R]

Originally posted by 2.7RACER
Scott,
You've got fuel and compression and no go bang.
What else is left?
If necessary switch primary wires to 5 & 6 at both ends.
Attach #5 wire to a plug outside of the motor and verify spark.
Check distributor cap. Double check firing order.
Make sure the wet plug is dry.

The cap is new, however I will most certinaly try a different cap right away, I had pulled the #5 wire in the past and checked for spark, it did spark, however I have no baseline for how intense that spark should be.

I'll check the plugs again as well, this has to be something I have been fighting for a LONG time, I just now noticed that it was the root cuase.

[stlrj]

Might be a bad spray pattern on injector #5. I would replace it.

Joe

[Elombard]

Also, this is way out there, I have a bad fuel accumulator on my CIS motor. It does not keep the pressure like it is supposed to. When the motor is hot some times I think I am getting vapor lock in a few of the fuel lines because of low residual pressure. It runs poorly for a while until it clears. IS it possible this is part of the problem? Check the spray pattern on hot start and see what it looks like (as mentioned above).

[Scott R]

Originally posted by stlrj
Might be a bad spray pattern on injector #5. I would replace it.

Joe

I did, this is the second new injector, and third injector that's been in that location. I have an old set of 951 injectors that were 29.5 lbs, versus the 30Lbs that I have currently.

[Early_S_Man]

Scott,

Check your #5 spark plug wire for end-to-end resistance??? When hot the CDI output Voltage is a bit lower than when cold. An open Beru connector will jump the gap when cold, but a miss will occur at high temps.

[Scott R]

Originally posted by Early_S_Man
Scott,

Check your #5 spark plug wire for end-to-end resistance??? When hot the CDI output Voltage is a bit lower than when cold. An open Beru connector will jump the gap when cold, but a miss will occur at high temps.

It's around 3 ohms cold, I'll do a hot test today.

[Early_S_Man]

3K Ohms is nominal if no resistance in the distributor connector, otherwise 4K Ohms. Check to see it is loose at the distributor cap, too.

[Scott R]

Originally posted by Early_S_Man
3K Ohms is nominal if no resistance in the distributor connector, otherwise 4K Ohms. Check to see it is loose at the distributor cap, too.

Uh oh. All six are around 3 Ohms, they are about a year old set of Bosch wires with Beru connectors.

[Elombard]

oops I see Tbitz, my bad thought you still had the CIS.

[Huh]

Are you sure you are using the correct injectors? A CIS injector? That sounds very much like a leaky injector. I have that problem on my Scirocco. It looses pressure in one injector and it takes a moment to repressurize it so you loose the cylinder for a little. I'd check the distributor to that injector and connections for slight leak. I agree with possible accumulator but that usually results in a very hard start or no start at all until the motor cools down.

[ruf-porsche]

Could be something in the FD for cylinder No.5 Do you have the plastic or steel fuel lines? If you have the plastic line just swap either No. 4 or 6 injector complete with the line and see if the problem doesn't reappear at the swapped cylinder.

Never mind didn't see that you are running efi and not CIS

On second thought, are you getting a signal to the injector when it is hot?

Maybe a glitch in the progarmming?

[Scott R]

Originally posted by Huh
Are you sure you are using the correct injectors? A CIS injector? That sounds very much like a leaky injector. I have that problem on my Scirocco. It looses pressure in one injector and it takes a moment to repressurize it so you loose the cylinder for a little. I'd check the distributor to that injector and connections for slight leak. I agree with possible accumulator but that usually results in a very hard start or no start at all until the motor cools down.

I should have said something, it's EFI with 30 lb injectors, that of course does not ruel out what your saying I did however try different EFI injectors to try and rule that out.

[Scott R]

Did a little work this evening, I got the car nice and hot and it starts to run worse the warmer it gets, to the point where its questionable that #5 is the only dead cylinder. So I removed the Bosch plug wires, and the new distro cap and replaced the wires with my original SC wires, and original cap. Well it fired up after that and my CO was reading -0.8% I had to rich it up, which is a first for me and the idle hunt was gone. I'll try and restart it again in about 1/2 an hour and let you guys know the results.

[Early_S_Man]

Well, chalk up another one for aftermarket wires!!!

Your originals are rebuildable. Re-use the ends, remove the braid, install new 7 mm wire by Belden, Packard, Accell, MSD, Magnecor, etc.

how to test plug wires w/ ohm meter?