dcolpitts

Just installed a refreshed engine in my 1979 US auto, When went to test cold start fuel fuel pressure I got a high reading of around 58 psi which is high. I believe shoud have around 42 psi, so went on to making a pressure adjustment at Wur, by tapping the pin slightly to lower cold start pressure. The pressure went higher as I tapped down. Any Ideas from you CIS gurus out there! Thanks

jwillman

Not sure if you did anything to the WUR but there is an oring in the WUR that when I replaced mine resolved my inability to adjust. See link in post #8.

https://rennlist.com/forums/928-foru...to-adjust.html

dr bob

Are you looking at the workshop manual for data? System pressure (set by the fuel pressure regulator in the fuel metering unit/distributor) should be 75.4 to 84.1 PSIG. Read this with the outlet block valve on your gauge kit CLOSED.

Control pressures, managed by the warm-up regulator:

at 50ºF: 17.4 to 23.2 PSIG
at 68ºF: 26.1 to 31.9 PSIG
at 86ºF: 35.5 to 40.6 PSIG
at 104ºF: 44.2 to 49.3 PSIG

Read these with the outlet valve on your gauge kit OPEN.

These warm-up pressures are from the WSM schedule for 1979 manual gearbox cars. The chart on page 25-6 is in metric units. I converted these to imperial units. You'll want to do the same to the chart for your automatic car. I happened to have the notes on the manual cars since that's what I was working on when I made them.

Warm-up pressures are tested with the heating element in the warm-up regulator disconnected.

You MUST have the correct gauge and plumbing adapters installed to accurately test these pressures. The gauge set connects at the OUTLET of the WUR in the plumbing that goes to the fuel metering unit/distributor, with a shut-off valve in the outlet.

You'll need a good CO analyzer or wide-band oxygen sensor and mixture gauge to accurately adjust the metering unit. Exhaust samples must be taken BEFORE/upstream of the catalysts.

dcolpitts

Thanks for responses, I have the tester connected right, also have wsm with pressure values. Fuel pump and flow check out, O-ring is correct size, Wur was rebuilt by the deloren site about a year ago, and previous engine worked great on it. Thought refreshed block might change settings but not at start up. Tested with engine off, fuel relay jumpered cold engine and with test valve open getting a reading of 59psi. I also flushed out both fuel lines back to FD to check for blockage. My question now would be would the outlet line of the wur going into FD at fuel pump pressure adjustment spring be blocked or patrially to effect wur? Sorry for rambling just frustrating, Thanks again for replies

Petza914

If the old engine was running well with the same fuel distributor and WUR you used on the new engine, did you try and start the new engine in the car using these same parts before adjusting the WUR, and if so, what engine running problem are you trying to solve? Or did you just check pressures before starting the motor? I would have tried running the engine before messing with the pin in the WUR if the other engine was running well.

dr bob

The basic fuel pressure is controlled by the regulator in the fuel metering unit/distributor. No directly affected by the WUR. The WUR controls pressure to the lower cavity in the FMU/distributor, bypassing excess pressure to the RETURN to the tank at the shared connection at the FMU/distributor. If that line is blocked, you'd see higher basic fuel pressure. You state that you checked both (control pressure and bypass) lines back to the FMU/distributor for blockage, so you shouldn't worry about those.


Age-related deterioration of the little brass screens in the two units seem to be among the biggest causes of problems in CIS systems. If the engine isn't run for a while, or if the two main components have been stored out of the car dry for a while, those screens would be suspect. They crumble into a fine dust that screws with orifices in the two units, and can collapse and partially block passages. Cars that are driven don't have the issues because they are continuously wetted by fuel, and air doesn't get to them. Those screens may also be left out either accidentally or on purpose when the pieces are off the car. That's not a real solution, in my opinion anyway.


I use a cute injection system cleaning canister that doubles as a "fuel" supply for testing pieces like a WUR. I use deodorized paint thinner as a test fluid so less chance of fire while playing, and can plug the test gauge into the outlet of the WUR and let the bypass just gather in the bottom of a bucket. Set the fuel supply pressure directly with the air pressure going into the canister just a little higher than the target, and manipulate that pressure once I'm sure the plumbing is OK. This way, you can make precise adjustments to the WUR out of the car, where it's easy and clean access. The gauge kit has quick disconnect fittings for the WUR connections that greatly simplify testing in the bucket and adjustment on the bench. A dishpan is ideal for the bench work....


I'll echo Pete's advice too. More damage is done by owner tinkering that anything else except dirt.

dcolpitts

Thanks again for replies, I had tried starting engine without testing because I had just swapped out cis system from a running car but with these systems it it seems not all that easy. After starting the enging ran poorly so the testing began. After removing wur and testing with a home made bench test it appears is not the wur. The line to the fuel distributor from the wur has been cleaned so that leads me to believe their is a blockage of sorts in the fuel distributor so I will pull it and get a rebuild. No telling the last time this was done. What got me started in this direction was the fact that i had installed Vacuum and Fuel pressure gauges in the car so it could give me a pulse of the condition of the system. I had done this 3 years earlier from reading this somewhere on this forum. Thanks Again, any suggestions on distributor rebuild

Petza914

928 International and 928 Motorsports both offer a FD rebuild service. When I had a problem with mine, it was the pressure valve in the FD that had gotten stuck. Maybe check that first.

This comes out, then a small magnetic pickup tool should retrieve the other piece. If the internal piece doesn't come out easily, that could be your issue. I eventually got mine out by spraying oil in there and letting it sit and soak.

dr bob

And a reminder for 'bench testing' the WUR-- you do need to apply vacuum to the manifold port while you test control pressure. Else the control pressure readings won't be accurate. This is tough with a mitivac or other hand-help pump, easier if you have a reservoir in their.

82EUROATM

Ok I’m back at it again and I hooked up the gauge directly in between the wur going in and I only get 45 psi. We hen I turn the key off and turn it back on it sometimes falls to zero and then builds back up but to only 45 psi. When I play with the tan box and open the injector it falls to zero. I had it running the other day and today it won’t start like before my question is how do I get the psi high enough to fire the injectors ?

82EUROATM

I have a question I took the wur out and pushed the round block off plate outward and the psi when to 50 psi. Should I push it out even more to get more than 50 psi.