Rest Pressure Results

[Quinn]

My car has a hot start problem that persists after replacing check valve, accumulator and PPR O-rings. It will eventually start with enough cranking, if the battery doesn't go dead first. It just passed a California smog test. So, I finally hooked up a pressure gauge and here are the results:

Primary Pressure - 5.1 Bar
Control Pressure @ 32C - 2.7 Bar
Control Pressure >40C - 3.3 Bar

Rest Pressure:
0 minutes - 42 psi
30 minutes - 36 psi
60 minutes - 34 psi
90 minutes - 32 psi

How do these numbers look?

One more question. Do the fuel injectors play any part in holding rest pressure? In other words, would a leaky injector result in low rest pressure results?

Any insight would be much appreciated, thanks.

[82DMC12]

I think the pressures look okay but if you have a leaky injector you could be losing fuel in one or more fuel lines causing difficult starting. It would be flooding that cylinder.

I would suggest removing all six injectors, pressurizing them without pushing down the air meter plate, make sure they are not dripping under pressure, then let them sit under rest pressure only with blue paper towels on each tip so you can see if any of them are leaking.

You can also do an injector spray pattern test afterwards.

Sent from my Pixel 6a using Tapatalk

[r00b]

If you do end up needing injectors you could get them from rock auto https://www.rockauto.com/en/moreinfo...t=6224&jsn=357

I'd stear clear of any parts from dmch.

[Bitsyncmaster]

I don't think your rest pressure is causing the hot start problem. I think your test values are normal.

I did do a test of one injector removed and it did not affect rest pressure values or times.

[Bitsyncmaster]

First thing I would try is unplug the CSV. If that does not work, try the plug swap. That would pretty much tell you if it's a fuel problem.

[Rich]

First thing I would try is unplug the CSV. If that does not work, try the plug swap. That would pretty much tell you if it's a fuel problem.

+1 on Dave's comments, both the one about the rest pressure test (pass) and the one about the cold start valve in case it's injecting fuel during hot starts, which it shouldn't do.

Unplug its connector for just the hot start test.

[axh174]

My car has a hot start problem that persists after replacing check valve, accumulator and PPR O-rings.

Did you replace the PPR O-ring with a regular rubber O-ring or an O-ring that can handle ethanol-based fuel?

I had a hot start problem that persisted until I replaced the PPR O-ring with a Viton (I think that was the material/brand) O-ring.

I've also been told that one needs to be very careful when installing that O-ring, as it can easily be nicked upon installation.

[Quinn]

Thank you for all the suggestions. I will try them out and report back.

[Quinn]

I pulled the injectors and did some flow tests into graduated cylinders. The volumes were all within a few milliliters of each other, but I did notice that one of the injectors continued to weep fuel after the pump was turned off. So, I decided to pull out the intake manifold and begin the process to change them out, since I already have a set of new injectors and spark plugs that I bought a few years ago. There were a couple other things I noticed in the process.

IMG_1562.jpg

My micro switch has this unusual fuse? or resistor? jumpered between the upper and lower wire. This was not present on the car in the youtube how-to video I was watching on the VOD. Does anybody might know what this is?

IMG_1561.jpg

There also seemed to be a lot of oil residue around cylinder #1. I don't think the oil is coming out of the valve cover, but that would make the most sense. In the second picture, you can see oil pooled up in the bolt recess. Is there anywhere else oil could be coming from in this location?

IMG_1563.jpg

IMG_1564.jpg

[David T]

That is unusual, there is not supposed to be a fuse there. The oil leak looks like it is coming out from the bolt, not the valve cover gasket (or maybe the valve cover has a crack in it by the bolt?). As for a leaky injector, they can often be cleaned and work fine. A leaky injector will not affect Rest Pressure all by itself. The mixture unit must also leak, letting fuel go to the injectors even though the sensor plate is all the way closed. Besides fuel volume, each injector must have a good spray pattern and they should all open at very close to the same pressure. All of the vendors offer to clean fuel injectors so don't throw your old ones away. If your injector seals are not soft and rubbery you should replace them or you will have a lot of vacuum leakage. Use new copper sealing washers and do not overtighten the banjo bolts. After replacing the injectors inspect very carefully for ANY fuel leakage. While you have the intake manifold off replace all of the rubber vacuum hoses underneath and the cooling system hoses and gaskets.