a4sfed928

Okay a little background information, I recently purchased an 82 Euro for the engine and I am trying to get it running in place before moving forward with any transplant operations.
It will start and run for a few seconds every time I crank it. Its not loosing ignition fire and the fuel pump is running as it stalls out so this leads me to the CIS fuel system.
A system pressure test shows high fuel pressure so I have been trying to find the reason and I think I have found the issue but I would like a sanity check before proceeding.

Here is the test I ran to come to the conclusion that the fuel return line is partially blocked. I removed the allen screw right above the fuel return line banjo bolt and screwed in a fuel pressure gauge into the hole to monitor the return line pressure.
I cranked the car and it started and ran for a few seconds and the fuel pressure gauge indicated over 100 psi.

First sanity check, is there any reason other than a blockage that there would be pressure on the return line?
I have removed the fuel sending unit when I cleaned out the tank and replaced the tank inlet screen so I know the return pipe is clean in the sending unit. My next step is going to be to bypass the stock return line back to the tank by running a temporary rubber fuel line back there.
Anyone see any issues with this process?

thanks
Brian.

The Forgotten On

Inside of the metering head there are small fuel screens that can get clogged, same for the WUR, and they can cause all kinds of pressure issues.

I would recommend removing them and making sure they are clean before chasing other issues.

Also, the running for a few seconds and then shutting off indicates the engine is only getting fuel form the cold start valve so your injectors are not opening.

a4sfed928

I replaced the fuel tank suction screen and the main fuel filter.
I temporary removed all the screens from the injector lines, replaced the fuel distributor inlet fitting with the screen in it and checked the WUR inlet screen and it was okay.

Are there anymore screens that I could have over looked?

a4sfed928

I also checked the fuel pressure regulator in the fuel distributor to make sure it wasn't stuck.

GlenL

You need to get a decent gauge set and apply it correctly to analyze the CIS. If you've done that, give the numbers. It's very doubtful that the return line is plugged. I don't follow what you're describing for a test at all. It's easy to screw up a CIS system by messing around with it. It can't be fixed by making adjustments. Those adjustments are for tuning when working well and will not correct for age, contamination or varnish.

jpitman2

Re "allen screw right above the fuel return line banjo bolt" - where is this? Dont recall an allen screw on the WUR. Disconnect the return line at the RHS cam cover, check that line is clear from there to the tank. As above get proper gauge set with open/close tap on one leg so you can see system and control pressures. System should be 75psi, cold control 15-25psi. Get a copy of Ben Watson book for troubleshooting. To diagnose control pressure high problems - with pump relay bridged (extinguisher handy) and pressure gauge fitted, crack open return line at WUR - if pressure drops, blockage is further along; if not, problem is in WUR. Crack open next joint at distributor - is pressure drops, problem is further along; if no drop, problem is behind .
If you see more than 75psi, sounds like a return problem, or main pressure regulator valve.
jp 83 Euro S AT 57k

Mrmerlin

it would be a whole lot easier to assist you if you posted pictures and descriptons of what your working on

a4sfed928

Okay the system pressure was greater that 100 psi checked at the WUR, it was pegging the gauge so I don't know the exact pressure because was afraid to let it fully pressurize.
I never checked the control pressure yet because without correct system pressure it doesn't matter.
I have checked the fuel pressure regulator at the fuel distributor by removing it and everything looks clean and it was not stuck.
There is an allen screw just above the fuel return line banjo bolt on the fuel distributor which is just like connecting the gauge in line with the banjo bolt. This will measure return line pressure which I assumed should be next to zero psi.
To my surprise it pegged the gauge again at 100 psi so it seems like I have a blocked return line.
I have removed the metal line that goes from the banjo bolt on the fuel distributor over to the flexible line at the passengers cam box and its clear.

I hope this clears up my thought process.

Brian

jpitman2

OK, more info is good. Have you checked the retuen line from the cam box to the tank is clear? If you pull the return line off the tank unit, and feed it into container, bridge the pump relay, do you get fuel flow? If yes, is it up to spec - 1350ml/30 secs ?
Back a bit - what started this process? Is the car running or not? If there is a problem, please advise what it is in detail. Check that you are fitting the gauge correctly, and reading PSI.
jp 83 Euro S AT 57k

a4sfed928

The return fuel tank return line is partially blocked, I ran the fuel flow test at the tank sending unit and I only get 400mL of flow in 30 seconds.
Bypassed the metal fuel return line by added a rubber line back to the fuel tank sending unit and the car will run now.

Is this a common issue and if so where is the most likely place the blockage happens?

Thanks

Brian.

jpitman2

First time I have heard of this line being a problem, so no idea where it might be. Check for damage or kinks in the pipe. Also try (with original pipe in circuit) loading the tank with Marvel Mystery or Berryman's oil, and bridgeing the pump relay for some time, to see it the moving fuel will scour out a blockage - if its dried fuel stuff that is the problem.
jp 83 Euro S AT 57k

a4sfed928

I inspected the line and there are no kinks or crushed areas so I am thinking dried fuel or corrosion.
Thanks to all for the advice.

Brian.

kiwiokie

I have read denatured alcohol, acetone or E85 + Sea Foam recirculated with a pump will remove varnish. Thinking I may need to do this on my ‘79 before I get it back on the road.

The Forgotten On

Have you checked the hose that goes into the fuel level sender? It can get kinked easily.

Also, the fuel level sender can get filled with crap and block the line as well.

karl ruiter

This is not an issue I have seen before (and I thought I had seen them all). Pulling the level sender seems like a good idea. The hose in the middle of it is the return line. One guess might be that someone replaced the level sender and left a twist or kink in the rubber line. If it is the metal line, and it is not dented in, you could either rooter it out, replace it with used, or replace it with plastic. I'm not quite sure if you could replace with used without pulling the rear cross member and tank. I have had good luck with the Dorman Nylon fuel hose. I think I used the 800-072. You heat up the end and the stock hose ends slip right in. It is very similar to what is the center of the stock rubber over plastic lines. I am uncomfortable using it for feed lines even though it is rated for that, and lots of new cars come with this style line, but on a return line I would be less worried.