Nathan

I just did 2 tests with the gauge hooked up between the fuel distributor and the WUR. The valve was on the WUR side. Everything was cold. It had been sitting for a day or 2 in the garage. I disconnected the WUR electrical plug. With the valve closed Friday evening, ambient around 85°, I read 1.9 bar. I opened the valve, WUR still unplugged, and the pressure jumped to 4.5 bar. I plugged the WUR and no change in pressure. I came back about an hour later and the pressure read about 1 bar, with the pump not running. I checked it again Saturday morning, ambient around 83°. With the WUR unplugged and the valve closed, I read 1.5 bar this time, and 4.5 bar with the valve open and the WUR not electrically connected.
1.5 bar seems low and the pressure jump without plugging in the WUR sounds odd too. What do you think my issue is?

Thanks for the help,
Nathan

MillenniumFalcon

How is the car running?

Nathan

I have been having a little hot start issue, and a slight idle issue, which may be a rich/lean adjustment. I have also noticed that when shifting up or down, the rpms dive. Sometimes the engine dies, sometimes it revs itself and stays running. The car is a '77.

Nathan

This is a better record of the test pressures:

87°F ambient, motor was not started during testing,

Valve closed pump running pressure is what? (system pressure) 4.5 bar

Valve open pump running pressure, wur unplugged pressure is?(cold control pressure) 1.6 bar

Valve open pump running wur plugged in pressure?(warm control pressure) took like 5 minutes to get there, but 2.3 bar

Valve open after warm pressure check, turn off car and residual pressure reading immediately and after 30, 60, 120 seconds and then 15 and 30 minutes? 1.4 bar immediately, 1 bar @ 30 secs, 1 bar @ 60 secs, .05 bar 120 secs, 0 bar @ 15 min, & 0 bar @ 30 min

MillenniumFalcon

I'm not sure that I would be looking at the WUR first as far as hot start problems or idle problems go, but I am no CIS guru. What kind of condition are the rubber intake manifold sleeves and injector/injector holder o-rings?

I noticed that on my car, as it idled, I could grab the injector lines right at the injector and pull up or push down firmly, and I would get a change in idle on a few cylinders. I will be changing my o-rings & injector holders. Also, my CIS airbox isolation mounts are broken or missing, and the entire assembly is being held up by the intake manifold rubbers, which now look awful and cracked.

Not saying your troubles are the same as mine, but I'd check for vacuum leaks before I would start testing the WUR. From what I understand, the WUR can often be laying there dead and the system can work just fine in anything but very cold weather....

As far as A/F mixture goes, I have no idea what mine is either, and I'm going to have to either buy/rent/borrow a portable A/F ratio device to set mine- I'll be pulling my CIS system out next week to change out all the rubber, o-rings, injectors, vacuum lines.

How long do you have to crank with the engine hot, before it will start? Have you gone through the ignition system already?

Nathan

Boots, orings, and ignition stuff is maybe 3 yrs old with about 5000miles on it. Cranking to get it to start is nothing. But i have to give it the gas to start and stay running for the hot start issue.

mfyoung1086

This is kinda tricky to answer with the info your providing... So you have a warm start issue, whats the FP reading when the motor is warm and you having the starting issues? That would help

Also on the hot start running rich, lean?

Nathan

I don't have a tool to be able to tell if I am running rich or lean either way. Per the tests above, after letting the pump run and the WUR plugged in for 5 min., I read 2.2 bar.

mfyoung1086

2.2 bar would be about right for a warm start, warm idle FP should be about 32 psi on these cars, which is about 2.2 bar, now when you're having these warm start issue, when you first try and start the car and its not starting well whats that FP? if its significantly under 32PSI than you might have an issue with the WUR, but like i said without FP readings from when the problem is happening i.e. when the motor is warm and you're having the start up issues I'm really just guessing.

Have you checked the accumulator yet?

mfyoung1086

Sounds like you might have a combo of problems. Check you warm control pressure, it sounds like your warm control pressure is low, causing a rich condition when you drive.

CIS systems really require access to a good CO meter, and long run it would be wise to install a wide band on your cars

But yes a improperly set AFR can cause CIS system to run poorly, but i think in your case it could be couple with vacuum leaks, or bypass air leaking from a faulty system

a WUR control pressure during a hot start should roughly be 3.2 bar, cold start could be anywhere from 1 to 1.8 bar depending on the system

Nathan rereading your posts, you FP from the pump is fine at 4.5 bar, you cold pressure is fine at 1.6, but if you motor temps were above 113F, and your warm pressure was 2.3, you running about a bar short on warm pressure meaning your running too rich

Nathan

The fuel accumulator is roughly 3 yrs and 5000 miles old. Excuse my ignorance, but what does AFR stand for?

mfyoung1086

Air/Fuel Ratio 14.7 is ideal, but no car really runs a 14.7 in real life usually in the 13's somewhere (rich), significantly below 13 is too rich, and above 14 is too lean

Have you tested the accumulator yet? I've had brand new Bosch O2 sensors dead out of the box (and yes I heated it up to test it ppls)

Simple test is the pull the return line off the bottom of the accumulator, pinch the hose, start the car and shut it off, if fuel runs out the bottom the diaphrem is gone and the acc. will need replacement

Now the acc. isn't the only thing that could be causing your FP bleed, you could have a bad check vavle... I'm not away of anyway (somebody tag in here) you can test the check valve to see whether its good or not, usually we'd just check the acc, if it didn't leak we'd replace the check valve and things would be business as usual. Now on VERY rare examples we'd lose the fuel distibutors, I've only seen it happen twice on prob the 100 CIS vehicles I've worked on, but they can leak and bleed pressure to the injectors.

You might have some combo problemo's to deal here with your CIS system, A) you're bleeding pressure, thats DEF causing hot start issues B) your warm control pressure seems low should be roughly 3.2 bar, which is more than likely causing your drivability issues

Nathan

I was trying to think of a CIS component with the acronym AFR, wasn't working. I'll check the accumulator this evening. I don't think my '77 has a check valve (separate of the fuel pump). My pump was replaced with the ignition stuff, injector orings, intake boots, fuel filter, accumulator - roughly 3 yrs & 5000 miles ago. What would be the culprit with the low warm control pressure?

mfyoung1086

I find this hard to believe A) WUR do more than modulate control pressure during warm up, the modulate control pressure constantly, and pre lambda they are vacuum operated to modulate control pressure under load

Ok I need to correct my own @ss here as well I double checked the warm control pressure for your car, 2.3 is within spec, the later models used 3.6ish my bad

Anyways I would still start with the check valve, you know it could be possible your return line is clogged as well

mfyoung1086

a 77 should have a check valve right on the output of the pump, if your acc. is still good I would replace the check valve next

Also one more thing to look at there is a thermal valve starting MY77, that if the circuit remains open will not allow the engine to lean out