Johninator

I'm having the problem on my 85 corvette. I will be driving and when it is at temperature (that's the only time I have seen it happen) it will fall right in its face, complete rpm drop when I get into it. I checked fuel pressure and a few times it would drop to about 20 just from twisting the throttle linkage on the TB. Have a brand new fuel pump and strainer on it. Also checked fuel filter it was completely clear so I put it back on. Plugs are still showing a lean condition last tike I checked. If the FPR goes bad, wouldn't I be seeing a rich condition? Other thing that is coming to mind would be one or more injectors. 30 year old injectors, probability is high on possible problem with them.

Just looking for everyone's opinion. Thank you

DanZ51

Just something to check: I was having a fuel pressure problem and I back flushed some compressed air from the (disassembled) fuel regulator and some kinda crap (RTV?) came out of the fuel rails. Not saying yours has contamination, but it's easy enough to blow some air through the disconnected fuel lines
.

Cliff Harris

You might have a bad connection at the fuel pump pulsator. This thing:

playsdixie

my 85 did the same thing...line coming out{and then back in] the pulsator....

Johninator

Is that located on the fuel pump assembly that comes out of the top of the tank? Or is that located in a different spot.

John A. Marker

The pulsator is located between the fuel pump and the fuel line. Many times if you have replaced the pump, the line to or from the pulsator will pull out and your only getting part of the fuel flow...the rest is spewed back into the tank. I would remove it and replace it with a piece of 3/8" fuel hoe and a two screw clamps.

Test your fuel pressure to see what happens. If when you turn on the key (do not start) the pressure should build to 36-39 psi. If it is much lower than this...most likely the pulsator. Or it the pressure immediately drops to zero...same thing.

Johninator

I'll have to pull that off and recheck everything in there.

One thing u did get a chance to check this morning was the FPR. I pulled off the vacuum line on it and smelled inside the line, and I am getting a slight gas smell. No gas visible in the line but I can smell gas. Is this normal, I wouldn't think so since the vacuum should be completely sealed from the fuel system. Perhaps this could be the cause or contributing to the problem? Maybe later today or tomorrow morning I will have time to pull the fuel assembly out of the tank and inspect everything.

John A. Marker

You need to find fuel in the vacuum line to the FPR. Try this.....take the hose vacuum line off the FPR and start the car. If the diaphragm if the FPR is I would think you would see a small amount of fuel coming out the fitting.

My guess is still the pulsator.

Cliff Harris

You don't need to start the car (which would result in fuel spewing out of the FPR if it's bad). Just turn on the ignition. That will cause the ECM to turn on the fuel pump for 2 seconds. That's long enough to find out if you have a problem without creating a new problem (fuel all over the place).

Johninator

I have pulled the vacuum line off while running and didn't see anything coming out. Is that gas smell in the lines normal? I wouldn't think it would be.

Also, I haven't had a chance to take the fuel pump assembly back out, but I was thinking. It seems to only do that drop of fuel pressure when it is warmed up to temperature or hotter. If it was the pulsator then wouldn't it do it all of the time and not only when it's at temperature or hotter?

383vett

Stick a mityvac on the vacuum line going to the fpr and see if it holds vacuum. You can also suck on the line, close it off with your tongue and see if it holds vacuum.

DanZ51

I was checking my FP regulator last week and I noticed my reg wouldn't hold vacuum with my Mityvac. Other than that it seemed to operate normal. No fuel leaking, fuel pressure rises with throttle. Not sure where is could be leaking (vacuum), but I guess I'll be investigating further if indeed it should hold Vacuum. It's an aftermarket adjustable unit bought some time ago.

Johninator

Haven't had a chance to tear into the vette yet, but I did just take it out for a spin for about 45 minutes tonight. It is feeling more sluggish the more I drive it. Plugs are showing lean. And it did the cuting out fuel drop multiple times in a row within half a second of eachother when I went into second to get onto the on ramp of the freeway.
All the spark plugs look exactly the same lean condition. So whatever is going on is going on for them all. So with that, I am not thinking it would be injector problem. If one or two was lean and the other weren't then possibly, but for them all to go at the same time, seems unlikely.
Their is the pulsator that I need to check as soon as I can, but can the FPR cause these symptoms? I mean that diaphragm in there is 30 years old. When it goes bad is lean a symptom or is rich a symptom? Are there any sensors on these enjoys that control fuel pressure or anything fuel related that could cause this? Im trying to think through what could cause this. Fuel is getting to the rails, new fuel pump, and filter is good. I am expecting the pulsator to be good because I am very **** when I do my repairs and I would have noticed the line being off. And I also had this problem before I replaced the pump. So that leads me to the fuel pressure regulator. That would control the pressure going to all the injectors. And like I said I don't see how all the injectors could go bad at once. But I'm sure there is a scenario where that could happen.

Opinions?
I'm thinking of just getting the rebuild kit for the FPR and then getting the adjustable cap for it. Since it is a good idea to do that anyways. Even if the problem is elsewhere I am still going to do it.

aklim

You said your pump is new. What did you replace it with? When doing that, did you remove the pulsator? I did with my Racetronix kit.

Any way you can crimp off the return line? If you pressurize it and the system holds pressure with the return line crimped off, I would think the fault lies elsewhere from the tank. FPR or injectors.

Is reading the plugs relevant? The ECM is supposed to adjust things so I would rather look at 02 sensor readings.

As to your injectors, IMO, they were junk the day your car was built. I tossed mine in the trash can which is the rightful place for Multec injectors. Get a rebuilt set if you are changing the FPR from FIC. I get all my injectors tested and rebuilt if necessary every 100K, diesel or gasoline vehicles. If they are powersports stuff, every 3-5 years.