Missing fuel pressure

[cattig]

I have a autometer FP guae in car and at 16 pounds of boost I am missing 3psi of fuel pressure.

FP set at 52psi base I get 65psi at 16 pounds of boost.

Any ideas as to what would cause this? vacuum leak, guage off, bad AFPR, or bad fuel pump?

Any advice would be great.

Thanks,
Chip

 

[CLONE]

Re: Missing fuel pressure

I have a autometer FP guae in car and at 16 pounds of boost I am missing 3psi of fuel pressure.

FP set at 52psi base I get 65psi at 16 pounds of boost.

Any ideas as to what would cause this? vacuum leak, guage off, bad AFPR, or bad fuel pump?

It could be all of the things you listed. I'd start by checking your vacuum lines or replacing them all if they are still original. Next I'd check your autometer gauge against a calibrated gauge. I'd guess the missing FP is in there.

If not, up the base FP and see if your FP goes up under boost accordingly. If not it could be the fuel pump, filter or lines. If everything else fails, open up the AFPR and see if it's ok.

 

[cattig]

I checked the vacuum lines from the manifold to the afpr and the map sensor and found a leak at the fitting for the afpr. I fixed that and still the same 3-4 psi of fuel missing.

I still have the origenal vacuum lines everywhere else.

A friend of mine has a high dollar fuel pressure guage garenteed to be within a quarter of a pound up or down. I will try this next and see what I get.

 

[cattig]

Checked fuel pressure with another guage. Getting the same reading on both guages.

When I changed the fuel pressure to 54 from 52 I still get 65 at 16 pounds of boost.

I have a walbro 255 high output fuel pump and the fuel filter was changed about 500 miles ago.

When I installed the fuel pump I acidently crimped the return line, but only slightly. I figured that this would not cause any problems because it was the return and not the feed.

Chip

 

[CLONE]

Make sure you have NO vacuum leaks. If you are absolutely sure that you don't have any leaks, then you need to look at why the pump/filter/lines are unable to supply enough FP to go above 65 at WOT. Whether it be a cheap filter (like fram), bad fuel pump, crimped or deteriorated lines, you didn't remove the pulsator (you did throw the pulsator away, right?), something like that.

 

[cattig]

I did throw away the pulsor.

I have no vacuum leaks in the lines comming off the manifold and going to the afpr and the map. I don't know about the rest. I need to check/replace the others.

I do get more fuel pressure then 65psi when the boost spikes form being lean. I have seen as much as 70 psi with 20-21 pounds of boost.

I used a puralator fuel filter from pep boys. Is there a better filter?

I am thinking of taking the afpr off and taking it apart to make sure everything is ok inside.

Chip