edgarcia737

I have been having some popping and backfiring issues. So I hooked up the fuel pressure test gauges. I had no residual pressure. OK, so I ordered a fuel accumulator and fuel filter. I installed the new fuel accumulator and filter. It started right up. I let it warm up and attempted to drive. I couldn't get pass idle without serious popping and backfiring.

I'm starting to think my injectors could be part of the problem.

Do I need to reconnect my test gauges up? Boy this can be frustrating.

Ed Garcia
1977 Carrera 3.0

Steve Weiner-Rennsport Systems

Ed,

To clarify, are you saying that you have no system pressure??? Did this start shortly after you refueled the car?

A piece of dirt may have dislodged and become stuck in the fuel pressure regulator at the side of the fuel distributor.

You didn't say how many miles are on your car and thats a key bit of information when troubleshooting such things.

Make certain the check valve at the outlet of the FP isn't stuck.

Make sure the fuel pump is making full pressure.

Remove the in-tank filter to see if its obstructed.

edgarcia737

Thanks for the reply.



I haven't checked the pressure yet. It may be the FP check valve. In tank filter? Is that a screen? How do I access it?

Let me back up. I am having some issues with my K Jetronic system. it has difficulty starting when warm. So I attached the test pressure gauges and found my system pressure is fine. But when I shut off the engine, pressure goes right to zero. OK, sounds like the accumulator. I simply replaced the fuel accumulator and fuel filter.

It started right up. I let it warm up and went to test drive and I couldn't get the engine pass idle without a lot of popping and backfiring. I didn't put the test gauges but I will today.

My frustration is, I put a "new" fuel filter and "new" accumulator on and it's worst.

72,000 miles on the motor.

Thanks again,

Ed Garcia

1977 Carrera 3.0

Steve Weiner-Rennsport Systems

Ed,

Thanks for the additional info.

The FP check valve is supposed to maintain pressure in the fuel lines (against the accumulator) after the pump's power is switched off. These are well known to fail, usually from dirt and/or rust.

The in-tank filter screen is accessed at the bottom of the tank. Look for a large internal hex plug at the bottom. These are not cleanable, you will need to replace it and its sealing ring (901.201.141.00 & 901.201.143.00), thus a splendid opportunity to flush the tank and see how much junk is in there.

Once you know the fuel system is totally clean, you can test the pump's pressure and volume.

edgarcia737

Thanks for the prompt reply. I will order an inlet filter and O ring today but I may also need a new fuel pump too.

Here are my pressure readings

I switched on fuel pump with electrical connection to WUR unplugged. The system pressure, valve closed read 120 psi. Whoa! that seems high to me.

Then I opened the valve at the "T" on the gauge set, and recorded WUR control pressure for cold engine (< 50 degrees outside air temp.) 60psi.

With the fuel pump still running, I plugged in electrical connector on WUR. I got no increase in pressure, valve still open. 60psi.

I turned off FP and system pressure slowly dropped to 10 psi for about 60 sec. and then to zero.

It's looking like the fuel pump may be one of the problems. I checked my thermo time switch and the resistance values seem to be correct.

Steve Weiner-Rennsport Systems

Looks like your FP may be all done.

Replace the in-tank filter first to make sure its not starving.

edgarcia737

Thanks Steve,
I agree. I just ordered a FP, in tank filter and O-ring. I'm leaving town in a couple of hours but home Christmas evening.

I guess Santa is bringing me a shiny new fuel pump

Steve Weiner-Rennsport Systems

You are quite welcome,..

Please let me know how everything works.

edgarcia737

Well here's an update.

I did replace the FP and my pressures were in limits. But still my residual pressure was zero. It should also be noted that my old FP was very noisy. I never realized how noisy it was until I installed the new pump.

But while I was adjusting the idle and idle mixture (with the air cleaner removed). I noticed a drop of fuel in the air box under the fuel distributor. That can't be good. So i increased and decreased the RPM several times. Again, a couple of drops of fuel in the air box dripping from the fuel distributor. I suspect that is why I have no residual "rest" pressure.

I'm half tempted to yank that CIS out and install PMO carbs.

I still need to replace the fuel tank inlet screen. I was hoping to drive around and run the fuel level down.

Tomorrow I'll call around to see what the rebuild cost for my CIS unit. It's soooo frustrating

Ed Garcia
1977 Carrera 3.0

Steve Weiner-Rennsport Systems

Ed,

Bear in mind that the FD and WUR is very unique to that model so if you send them out for rebuilding, make sure you get your components back.

edgarcia737

Thanks Steve. I'm sending the fuel distributor to Fuel Injection Corp to have it benched tested. I am certain that my WUR is fine.

edgarcia737

Here's the update.

I sent my FD to Fuel Injection Corp. Great bunch of guys. They benched tested my FD and made the repairs and promptly sent the unit back.

I just reinstalled the unit and everything is back to normal. Starts right up and runs great. It should be noted that I also replaced my injectors too.

So if you are having CIS issues. Give Fuel Injection Corp a call.

Ed Garcia
1977 Carrera 3.0

GothingNC

Glad you got it sorted out

John