Fuel delivery problem?

Mister P · Mister P's Garage

Got my 83 911SC out of winter storage and took it for a short drive. Next morning car would start up but then sputter out. This happened before (about 15,000 miles ago) and I ended up replacing the fuel pump, fuel filter, fuel accumulator, and relay only to find that the problem was with the pop-off valve in the air box (had come unglued causing a loss of compression). I checked the pop-off valve and that is still intact, so I ordered and installed a new fuel filter this morning. The car started up, ran for about 10 minutes, then sputtered out again. I don't want to buy another fuel accumulator if the problem lies somewhere else. Not being a mechanic, does anyone have any other suggestions as to what the problem might be?

E Sully · E Sully's Garage

Have you ever checked the fuel strainer in the bottom of the gas tank?
Part #: 911-201-141-00-M100
Tank needs to be near empty to check since it is at the bottom of the tank.

Mister P · Mister P's Garage

Thanks for the suggestion, Ed. I'll give that a try.

Mister P · Mister P's Garage

Of course I just filled the tank before putting it in storage. Going to have to figure out a way to drain the tank in my driveway since I can't drive it........lol.

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Mister P

Got my 83 911SC out of winter storage and took it for a short drive. Next morning car would start up but then sputter out. This happened before (about 15,000 miles ago) and I ended up replacing the fuel pump, fuel filter, fuel accumulator, and relay only to find that the problem was with the pop-off valve in the air box (had come unglued causing a loss of compression). I checked the pop-off valve and that is still intact, so I ordered and installed a new fuel filter this morning. The car started up, ran for about 10 minutes, then sputtered out again. I don't want to buy another fuel accumulator if the problem lies somewhere else. Not being a mechanic, does anyone have any other suggestions as to what the problem might be?

Mister P,

If you suspect that the problem could be your fuel delivery, there are several easy ways to test it. Here are some:
a). If you have a fuel pressure gauge use it. It will tell you if the pump is the culprit or the fuel supply.
b). Flow rate test. Do you know how to test run the fuel pump of your CIS? If you do, disconnect the fuel line before the fuel accumulator and measure the volumetric flow rate by running the FP. If you get 1 liter per 30 sec. or 2 liter per min., you have sufficient flow rate.

If the flow rate is less, there could be a reason for that. Either the FP is bad or not getting sufficient fuel from the gas tank. The FP is easy and simple to test. Checking the fuel tank filter requires more effort and time specially if you have more than half talk of fuel to drain.

Tony

Sailkane · Sailkane's Garage

First place to start and easiest...find fuel relay in front trunk fuse box. Have someone put a finger on it and some one turn key on ( not starting) you should feel relay pick up and when they turn off the key then it will drop out. If this works then do the same at the fuel pump.

E Sully · E Sully's Garage

I've heard of the infamous red fuel pump relay. It doesn't come to mind for me since that was added in later CIS models, mine is a direct feed. I would agree to check the relay and it's socket. I've read that the relay holder pins can cause poor connections with age.
I still say to check the screen in the bottom of the tank as soon as you are able. If fuel does not flow out of the tank, it can burn out the fuel pump since they use the gas flow to cool it.

Mister P · Mister P's Garage

Just after posting the first thread, I went out and the car started right up. I thought by some miracle that my tinkering had somehow solved the problem. I started it and let it run several times before feeling confident that I could drive it. Took it around the block once successfully and tried a second time. As I started to slow down for the red light, car stalled and would not start. Neighbor helped me tow it into driveway. I have installed a new relay (says for fuel pump but is the same part number as the multi-purpose relay), drained the gas tank and replaced the gas tank filter, tested the fuel pump (just that it was working but didn't have the equipment to test the flow rate) , and replaced the fuel filter. I guess I'm going to have to figure out how to do the flow rate test that Tony recommended. Any other thoughts or suggestions? If not a fuel problem what else could it be? I really appreciate all of your suggestions, Thank You!

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Mister P

Just after posting the first thread, I went out and the car started right up. I thought by some miracle that my tinkering had somehow solved the problem. I started it and let it run several times before feeling confident that I could drive it. Took it around the block once successfully and tried a second time. As I started to slow down for the red light, car stalled and would not start. Neighbor helped me tow it into driveway. I have installed a new relay (says for fuel pump but is the same part number as the multi-purpose relay), drained the gas tank and replaced the gas tank filter, tested the fuel pump (just that it was working but didn't have the equipment to test the flow rate) , and replaced the fuel filter. I guess I'm going to have to figure out how to do the flow rate test that Tony recommended. Any other thoughts or suggestions? If not a fuel problem what else could it be? I really appreciate all of your suggestions, Thank You!

Paul,

There are several things that could contribute to your no-start problem/s. And you will not know it until you perform some diagnostic tests to identify the most likely culprits. Some people like to suggest replacing parts and sometimes they get lucky. I don’t replace parts unless tested and confirmed defective. Most common suggestion today is to replace the fuel filter and fuel accumulator. And if that did not fix the problem, what do you replace next?

When you visit your medical doctor for a physical check up, what is the first thing they check on you? The nurse checks your pressure and your weight before even asking why are you here at the clinic.

Similarly, when I diagnose a CIS engine, I need to know the following:
a). Fuel pressures (CCP, WCP, SP, and RP).
b). Does it start at all? What problem are you experiencing.
c). Etc.

Lastly, a fuel pressure gauge kit is a mandatory tool for troubleshooting fuel injection system regardless what type you have. Without one, you are wasting a lot of your time doing guess-work troubleshooting.

Tony

Mister P · Mister P's Garage

Apparently it takes a few attempts at starting the engine to "prime" the fuel system after replacing the gas tank filter and fuel filter? After several failed start-up attempts the car started and has been running fine ever since. I am still going to take Tony's suggestion and pick up a fuel pressure gauge and check out the fuel injection system. Thank you all so much for all of the valuable suggestions offered.