Warm start issue

[bytes311]

Hi David: I did just that this morning after reading your response. I located a shop in town that work on Volvo engines and can clean/test injectors.

[bytes311]

Got my injectors back. The shop said they back-flushed the injectors and all of them had a good atomized spray pattern. I put them them back on my car and jumpered the RPM relay to witness the spray pattern for myself but none of the injectors cracked open with the plate depressed. The car starts and runs just fine though. Weird. I restarted the car several times while warm and it fired up every time. Fingers crossed dirty injectors was the issue.

[bytes311]

Sorry to bring this topic back up. I'm still trying to figure out if I have issues with my fuel injectors.

After sending the injectors off to have them cleaned and then put back on my car, my engine runs and sounds great. No loss of power. No misfire. But when I tried to perform the injector spray test again with the RPM relay jumped, only three injectors cracked at the same time. Two injectors seem to switch off between each other, for example: depending how hard I press on the air plate, one injector sprays while the other is dry, and vice-versa. It's as if there's not enough fuel pressure in the system to crack open all six injectors at once. I have Hervey's aftermarket fuel pump, and I don't know what the PSI rating is. There are no fuel leaks as far as I can tell, and I just changed the PPR o-ring last week which cured my hot start problem. With all of the injectors taken off the lines, I get the same amount of fuel at each line.

[David T]

If they cleaned and tested the injectors correctly with the right cleaner/tester,they should have tested the opening (cracking) pressure. You can never get them all to work exactly the same but they can be close. I doubt that is the problem. Exactly what is the symptom you are experiencing when you say you have a warm start problem? If you have the classic hot restart problem and the plug swap gets you going, you are going to have to figure out why you are not holding rest pressure. You could get a fuel gauge to confirm but we already know you aren't holding rest pressure long enough. It is going to be (in order of probability)

Accumulator
Fuel pump check valve (especially if you have the newer style DMCH pump)
PPR
Leaks

If you don't hold rest pressure long enough for the motor to cool to the point the Cold Start Valve operates you experience the hard hot restart and by doing the plug swap you force the cold start valve to operate, getting you started. Holding rest pressure while hot prevents the fuel from vaporizing in the lines and gets the injectors to open a lot faster.

[bytes311]

Hi David,

My warm start issues went away after cleaning the injectors and replacing the PPR o-rings.

I'm just confused why only three injectors open when I do the spray test, but then my engine runs and sounds perfect, with no telltale signs that some cylinders are not getting fuel. Is fuel pressure higher with the engine running vs when the pump and relay is jumpered?

[Bitsyncmaster]

Hi David,

My warm start issues went away after cleaning the injectors and replacing the PPR o-rings.

I'm just confused why only three injectors open when I do the spray test, but then my engine runs and sounds perfect, with no telltale signs that some cylinders are not getting fuel. Is fuel pressure higher with the engine running vs when the pump and relay is jumpered?

I've seen those problems if I pressed the air plate to far. I don't think the air plate ever goes to the bottom of it's movement during normal engine running. I usually just press the air plate about half way down when testing injectors.

[Miles]

You should be able to test the accumulator by switching the ignition on until you hear the pump prime the system, then see if it's easy to push the sensor plate down.

[Ron]

My warm start issues went away after cleaning the injectors and replacing the PPR o-rings.

I'm just confused why only three injectors open when I do the spray test, but then my engine runs and sounds perfect, with no telltale signs that some cylinders are not getting fuel. Is fuel pressure higher with the engine running vs when the pump and relay is jumpered?

Like David said, the injectors don't open at exactly the same time. Also, when they first open, they are not delivering at the same rate as when it's idling -- At idle, the rate is slightly higher, at which point they will be even enough...

Nope, the PPR holds the same pressure running or not.

Sounds like she's good to go to me...

[bytes311]

Like David said, the injectors don't open at exactly the same time. Also, when they first open, they are not delivering at the same rate as when it's idling -- At idle, the rate is slightly higher, at which point they will be even enough...

Sounds like she's good to go to me...

That's good to hear!

[David T]

If you feel the injectors are still not good you can try using a can of Techron to clean them up some more. If you have fixed your hard hot restart and you can get into closed loop and adjust the dwell right you are "good to go".