I'm like Tony . i like to use the tools to identify as much as possible before using the parts shotgun ..

But tony i do have one question that maybe you answered here that i'm just missing . Lets say you are measuring residual and it is dropping, much like we suspect. What troubleshooting can you use to isolate whether it is the FP check valve or the accumulator that has failed ?

FP check valve is a huge PITA and the accumulator is expensive . Neither job i would want to do without knowing for sure.

TIA

Had the exact same problems you describe and it was the fuel accumulator for my 1981 SC.

CIS troubleshooting........
 

theiceman,

Identifying the source of residual fuel pressure loss is done by isolating the suspect component and do a pressure test. For example, checking FP check valve in situ:
1). Install a pressure gauge kit with a shut-off along the main fuel delivery line.
2). A suitable location is before the fuel accumulator. Install the pressure gauge with shut-off valve in series.
3). Test run the FP for several seconds and switched it off and immediately shutoff the the valve.
4). Record the pressure reading on the gauge after closing the valve. Record the pressure reading on the gauge after 10, 20, and 30 mins. Refer to residual fuel pressure data in the manual and compare your data.
5). If the residual fuel pressure is below the specification, you found the culprit. However, if it passed the test move on to the next test.

Testing the fuel accumulator in situ:
1). Install the pressure gauge kit after the fuel accumulator. Repeat the above test. If the fuel accumulator is not leaking, you will get the same test results.

The fuel accumulator could be easily tested on the bench too. Place the FA in a glass filled half way with water or enough water to submerge 50% of the FA in water. Manually blow air to one of the top ports and blocking the other one with your thumb or a rubber stopper. Air bubbles will be coming out from the water if the FA is defective.

There is another culprit that you may like to test too. The FD primary pressure regulator. But we will defer the discussion on this because the earlier FD models are different from the later one found in SC’s.

You will often read people saying “I replaced the fuel accumulator and fixed the problem”. That is well and good if the culprit was the FA. I don’t recommend replacing CIS components which are expensive without testing and verifying to be bad or defective. Unless you don’t care to spend unnecessarily.

Tony

great info Tony, so basically you are just moving the shutoff between the accumulator and the FP . very good thanks

i never thought if using my CIS pressure gauges beyond the basic system, pressure control pressure, and residual pressure checks

I will have to keep this on in mind

Thanks again .