Fuel Mixture Problems - Car won't start when mixture set properly

[spikeygg]

I took that top hose off and was able to slightly lift the FD. The plunger seems to be very smooth but I can't lift the FD high enough to assess the o-ring status. The screws holding the FD on were fairly loose. The o2 sensor is brand new.

[Ron]

FWIW I just now watched the Dwell meter vid. You got no action going on there at all.

I was thinking the same thing. It seems it only reacts when the throttle is hit and even then it fluctuates in a range way above 20 (while it clears out).
I'm thinking hang on to the parts money until the pressures are checked, then set the CO and go from there. ...then tweak it a little off spec to compensate for the cams if needed.

[spikeygg]

I asked my girl to come handle the camera while I held the beast up so I could get a good view of it. Here's the result:

PXL_20210829_163019826.jpg

It's pretty grungy under there. The plunger is quite loose and wants to drop out as I lift the distributor up. I noticed it has a couple of spots on it (looks like rust?) but dunno if that's an issue or not. I'd like to clean all the dirt off but I'm worried about wiping it into the intake since I can't just move the distributor out of the way. For now I put it back down, buttoned it all up, and keyed on to run the pump a few times. When I get the pressure tester, I'm hoping I'll have a better idea of how stuff looks.

EDIT: Haha, I guess this stupid dmctalk forum thought it would be better if the picture was upside down. :-/ The pictures I took were the other way 'round.

[David T]

If the plunger can move freely without sticking LEAVE IT ALONE! Assuming the car ran OK before your problems my guess is a vacuum leak (or leaks). You tried to "fix" it by adjusting the mixture and that got it to run better but only at idle. After-market cams make the motor even more sensitive to vacuum leaks, especially at idle since you don't produce much vacuum at idle. Because of the vacuum leaks you lean out once you go off-idle and the adjustment you did won't help. You ONLY touch that idle screw once you KNOW there are NO vacuum leaks and everything else is perfect. The mixture only changes because you get vacuum leaks, not because the adjustment changed.

[spikeygg]

Where should I hook up the fuel pressure tester? Do I put it in line between the fuel filter and fuel distributor?

[Ron]

FWIW, instructions should come with the gauge.

PressureGaugeHookUp.jpg

[spikeygg]

FWIW, instructions should come with the gauge.

PressureGaugeHookUp.jpg

Thanks @Ron! That's what I needed. The instructions that came with the thing are terrible... I'm pretty sure this was written by Chinese.

[spikeygg]

Okay, with the tool I bought I was only able to measure the pressure at a single point (instead of running it in-line). It came with a bunch of fittings but none of them worked for putting the device in-line. So, all I was able to get was the pressure at the top of the fuel distributor that goes to the CPR during engine operation. It was static at 45psi, slightly over 3bar, I hooked up the dwell meter and it was static at ~8º (engine cold). I revved it periodically to help keep the exhaust temps up until it was warmed up and then the dwell meter ran like this:



When I keyed the engine off, the pressure at the top of the distributor bled down very quickly: from 45psi to 0psi in about 15 seconds. So, clearly there's a leak somewhere, but it isn't on the outside of the engine because I didn't see or smell fuel anywhere.

What's the best way to determine where the leak is coming from?

Should the top of the FD be fixed at 45psi?

Where should the dwell meter oscillate? If I'm reading the workshop manual correctly 35º-45º, is that like this:
Dwell_Reading_Expectations.jpg

I think I'm going to return this pressure tester and try to get a kit that I can mount in-line because I want to be able to shut off the return feed and get the max pressure, like it showed in Ron's attachment.

[Ron]

Okay, with the tool I bought I was only able to measure the pressure at a single point (instead of running it in-line). It came with a bunch of fittings but none of them worked for putting the device in-line. So, all I was able to get was the pressure at the top of the fuel distributor that goes to the CPR during engine operation. It was static at 45psi, slightly over 3bar, I hooked up the dwell meter and it was static at ~8º (engine cold). I revved it periodically to help keep the exhaust temps up until it was warmed up and then the dwell meter ran like this:


When I keyed the engine off, the pressure at the top of the distributor bled down very quickly: from 45psi to 0psi in about 15 seconds. So, clearly there's a leak somewhere, but it isn't on the outside of the engine because I didn't see or smell fuel anywhere.

What's the best way to determine where the leak is coming from?

Should the top of the FD be fixed at 45psi?

Where should the dwell meter oscillate? If I'm reading the workshop manual correctly 35º-45º, is that like this:


I think I'm going to return this pressure tester and try to get a kit that I can mount in-line because I want to be able to shut off the return feed and get the max pressure, like it showed in Ron's attachment.

Connecting your gauge to the top of the distributor is the same as shutting the valve on the correct type of gauge. That should show primary pressure ("max pressure"). It should be 71-79 psi (WSM D:02:01). I would double check then suspect the PPR. ...If you still have no rest pressure after fixing that, I would suspect the accumulator.
Also, note that there is another o-ring in the PPR not shown in the pic above (which does not come in some of the 'warm up repair kits').

For dwell, you need to use the 8 cylinder scale and divide by 2...so it should oscillate across 20º, on eight cylinder scale.

[spikeygg]

@Ron, the stock fuel circuit was still complete with the gauge installed. I used the gauge set's banjo bolt replacement that added a quick disconnect for the gauge so it shouldn't be with the valve shut.