on my 87 trans am I am having a strange issue that started the other day...

under load and at wot the RPM's go to 2500 and then the car bogs out and nearly stalls

I replaced multiple parts since I had a nearly new dizzy from a parts car I swapped the whole thing to replace the pickup coil, ICM, cap, rotor, and wires are newer. Engine had new plugs after the swap to the 350.

My car has been running pretty well for the last month or so when I got it out and now this suddenly happened.

Only other thing I noticed was the fuel pressure primes to ~40 psi when the key is turned but drops to ~25 in less than 30 seconds. I have to try to test the pressure with the return blocked tomorrow. I'm hoping someone has cured this problem and can offer insight as to whether its is a fuel or spark issue

Thanks in advance

 

Well O had a chance to check the fuel pressure on the car. As I stated originally the fuel pressure drops pressure drastically after the pump primes. I taped up the fuel pressure gauge I was using to the windshield and had my passenger watch the pressure.

Idle : ~32 psi
1/2 Throttle : 36 psi
WOT : ~15 psi

The pressure drops down to 15 or a bit below where the engine bogs and dies out under wide open throttle under load.

My main question now is whats the best way to determine if this is a weak pump or bad regulator?

 

If you check the vacuum line on the regulator, you should not have any gas in the line. Gas in the little vacuum line can sometimes be a symptom of a bad regulator. How is your fuel filter and has it been changed? If no fuel in the regulator vacuum line and the fuel filter has been changed lately, my guess would be the fuel pump.

 

I had the vacuum line off before and there was not fuel in the line. Filter is going to be changed soon before I do either bigger project

 

Sounds like the pump may be going out.

 

Where would you guys recommend getting a replacement pump? I think this would be the more likely because when I clamped the return line the pressure only went to 42 psi.

If I have to change it I may be changing the whole unit because my gauge doesn't work on the dash. ( tested by grounding the pin in the connector and gauge went to empty )

 

Walbro or Aeromotive are good pumps, I would look at going a little bigger than stock on the pump for future engine projects, unless stock is good enough for you. And i also would suggest dropping the tank instead of cutting a access hole from the top. I just replaced mine, and it really was not that bad of a job. Siphon or drain most of the gas out first.

 

Definitely going to drop the tank to do the replacement, the rear end is making a 'clunk' so it has to come out anyway soon.

Any thoughts on replacing the sending unit itself? or can it be repaired?

 

I have never had to work on that. I think I would try to see if it's a fuse or a bad wire, or maybe when you drop the tank, you will find the ground has went bad. The whole assembly is grounded inside on the bracket and also on the outside of the top of the fuel sender unit. Or, maybe even the float fell off inside.

 

Well I started with the cheapest/easiest repair and did the fuel filter. The filter I removed was actually loose inside and rattled when I took it off

I figured maybe this was part of my problem but I put the new filter on and the car is still cutting out and has very little power.

Most likely I will be looking into doing the pump next...

 

What brand of fuel filter was it? They shouldn't rattle. At least I have never had one rattle. You keep at it 2012sergen11 the mechanic, you'll fix it.

 

I believe the filter I took off was a Fram but not 100% sure.

Never hadid one rattle either which is why I thought I found the issue bud sadly not