Warm start issue

[bytes311]

I have a strange warm/hot start issue that I can't seem to figure out.

If I shut the car off after the engine warms up and then try to immediately restart it, it cranks and cranks as though it's not getting enough fuel. I can hear (and feel) the pump prime. If I perform the plug swap, the engine starts right up. But then as soon as I shut off the engine and try to restart it again, same situation.

I pulled out my dwell meter and the A/F ratio is within spec. The FV buzzes just fine. The accumulator is two years old, but it IS the later, smaller-styled one. No kinks in the lines from what I can tell.

Do our gas tanks pressurize? Because the gas cap that I have doesn't lock or tighten. I ask because I'm wondering if the problem is with the (Hervey) fuel pump. Maybe it's not creating enough pressure to suck fuel through the lines? I don't know.. I'm kinda grasping and straws now.

Thanks!

[David T]

If you do the "plug swap" and it gets you started, hot, you have a rest pressure problem. It could be the check valve by the fuel pump, the "O" rings in the PPR, or the accumulator. The small one should be OK but if you have a leaky check valve or PPR it cannot hold the rest pressure up long enough.

[NckT]

You'll need to do a fuel pressure test.
This will indicate if when you turn the engine off, what the test pressure is.

If the fuel pressure is lost quick then you've got a problem with the fueling as it should retain rest pressure of half shut off pressure after 10 minutes.

Assuming that the "new smaller" accumulator is sized to oem capacitance, then the usual suspect is the O rings on the fuel distributor primary pressure regulator, or the check valve (one way non return valve) from the outlet of the fuel pump has failed, causing the accumulator to dump pressure back in to the petrol tank.

It's not scientific, but if the accumulator goes "boing boing boing" as the spring presses the diaphragm releasing the fuel slowly then there is the greater chance it's the O ring not the check valve. This isn't always accurate though !

It's cheaper and easier to change the O rings than the check valve.

The above assumes that the new accumulator is working fine and fit for purpose, as I would always stick to oem specification.

I hope it's an easy fix for you.

Nick

[bytes311]

Hmm okay, so it could possibly be related to leaky fuel pressure? Even if I shut the engine and attempt to start it within a few seconds?

I initially suspected it to be fuel pressure, but wasn't positive because there was a good amount of resistance on the air flow meter. I tried pressing down on the metering plate a few times to get it to "prime", but the engine still wouldn't kick over.

[Bitsyncmaster]

No start after a few seconds of shut down would not be caused by rest pressure loss. But the fact you got it started using the plug swap does indicate you are not getting fuel via the FD. I agree you need to start testing fuel pressure. I would also suggest you test that fuel pressure on the hot engine. Verify primary pressure around 75 psi and control pressure around 50 psi on that hot engine.

[bytes311]

Thank you all for your suggestions.

[Jonathan]

Would a sticky plunger in the FD cause this?

If the air plate is on the other end of the lever arm that goes up and down in unison with the FD plunger, then maybe what is happening is it gets stuck in position when the engine is turned off? Then it only gets going again once the plug swap sends fuel into the engine via the cold start valve and unsticks itself because of the air pulling in?

Is any of that even possible?

[bytes311]

Just want to follow up on this issue.

I pulled out all the injectors and jumpered the RPM relay to perform the spray pattern test. Two injectors (one on each side) didn't crack open. I swapped one of the bad ones with a known good one and it sprayed. I'm going to get them cleaned up and that'll hopefully resolve my issue. I'm not sure how long they've been this way, because I've never had any issues with idle, or full-throttle responsiveness.

[bytes311]

Looks like I need a new set of injectors. I tried blowing them out with a can of seafoam and a compressor, which did appear to work because the fluid atomized out of the nozzle, but the pressure may have been too strong because now the injectors wont crack open with the RPM relay jumped and the throttle plate pushed down. <sigh>

[David T]

The injectors can't be cleaned that way. You need to send them out to a Delorean vendor or find a Volvo dealer that has the tester/cleaner. Try to have them cleaned, it is a lot cheaper than replacing all of them.