Heat problem resulting in vapor lock? Bad fuel pump? Bad gas?
08-26-2007, 04:01 PM
#1
Drifting
Thread Starter
Heat problem resulting in vapor lock? Bad fuel pump? Bad gas?
Problem with the car and I am hoping for some help in diagnosing. Here are the symptoms:
When I start the car, fuel pressure is around 6psi (which I believe is adequate for my engine (Jasper 383...nothing exotic about it though) but as I drive the car, the engine comes to operating temperature, the fuel pressure steadily drops to 5...4...3...and even lower. If I stop the car, it is extremely hard to start. I am not driving it hard and only a few short stop lights over the 4+ drive I just took it on.
So I shut down, let it sit....the longer I let is sit. Easier it starts back up and has better fuel pressure. If I try to start up immediately, it cranks and cranks but nothing which seems to be only because of the low fule pressure.
I also tried letting it sit with the hood open, does the same thing. I start the car up, runs fine and you can watch over a period of minutes as the fuel pressure drops.
A few other (maybe) pertinent details:
1. It is freakin' hot and muggy in NoVa...Around 90-100 degrees lately and very humid.
2. Ran the car in a 4th of July parade and experienced vapor lock towards the end....Also fried my starter in the process but that has been replaced.
3. Had the fuel pump replaced not too long ago (maybe 2-3 months and the car has not been driven all that often)
4. I have a fuel pressure regulator / gauge in between the fuel pump and the carb
5. Gas tank was replaced same time as fuel pump and all of the hoses at the same time
6. Checked inline filter by carb and it is clean
7. I have Jet Hot coated hooker headers
8. In 3 years I have been driving this car, never had this problem and I have always driven it even in days as hot as this.
9. Engine temp stays in 180-195 range...electric fans are coming on and everything appears fine there as well.
Hope this is enough information and hope someone can provide me some good information....My #1 guess is some degree of vapor lock but then why have I not had this problem before? Could it be exacerbated by bad gas or the 4th of July parade incident?
Thanks in advance....
Shane
When I start the car, fuel pressure is around 6psi (which I believe is adequate for my engine (Jasper 383...nothing exotic about it though) but as I drive the car, the engine comes to operating temperature, the fuel pressure steadily drops to 5...4...3...and even lower. If I stop the car, it is extremely hard to start. I am not driving it hard and only a few short stop lights over the 4+ drive I just took it on.
So I shut down, let it sit....the longer I let is sit. Easier it starts back up and has better fuel pressure. If I try to start up immediately, it cranks and cranks but nothing which seems to be only because of the low fule pressure.
I also tried letting it sit with the hood open, does the same thing. I start the car up, runs fine and you can watch over a period of minutes as the fuel pressure drops.
A few other (maybe) pertinent details:
1. It is freakin' hot and muggy in NoVa...Around 90-100 degrees lately and very humid.
2. Ran the car in a 4th of July parade and experienced vapor lock towards the end....Also fried my starter in the process but that has been replaced.
3. Had the fuel pump replaced not too long ago (maybe 2-3 months and the car has not been driven all that often)
4. I have a fuel pressure regulator / gauge in between the fuel pump and the carb
5. Gas tank was replaced same time as fuel pump and all of the hoses at the same time
6. Checked inline filter by carb and it is clean
7. I have Jet Hot coated hooker headers
8. In 3 years I have been driving this car, never had this problem and I have always driven it even in days as hot as this.
9. Engine temp stays in 180-195 range...electric fans are coming on and everything appears fine there as well.
Hope this is enough information and hope someone can provide me some good information....My #1 guess is some degree of vapor lock but then why have I not had this problem before? Could it be exacerbated by bad gas or the 4th of July parade incident?
Thanks in advance....
Shane
08-26-2007, 06:31 PM
#9
Drifting
Thread Starter
Coming off of the fuel pump? No. Two 90 deg fittings.
Can I ask your line of thinking? What you think may be a problem? Unfortunately, we have guests coming over so I can not do the ice on the fuel pump. Do fuel pumps really overheat and lose pressure?
Could I have cooked the seals or something in the pump during the parade incident?
Thanks
Shane
Can I ask your line of thinking? What you think may be a problem? Unfortunately, we have guests coming over so I can not do the ice on the fuel pump. Do fuel pumps really overheat and lose pressure?
Could I have cooked the seals or something in the pump during the parade incident?
Thanks
Shane
Last edited by ShaneLU97; 08-26-2007 at 06:34 PM.
08-26-2007, 07:46 PM
#12
Drifting
Thread Starter
08-27-2007, 05:19 AM
#13
Race Director
on my 72 the PO disconnected the return, thinking is was an emission control.
hot day in a traffic jam it died, was hard to start.
i hooked it up. that was 1991.
no problem since.
it is a clue for u,
numerous possibilities on old cars
good luck!
hot day in a traffic jam it died, was hard to start.
i hooked it up. that was 1991.
no problem since.
it is a clue for u,
numerous possibilities on old cars
good luck!
Last edited by Matt Gruber; 08-27-2007 at 05:23 AM.
08-27-2007, 09:20 AM
#14
Race Director
Some possibilities:
Bad pickup sock in tank
Kinked fuel hose at tank or pump.
Bad pump (I know, its new. But sometimes NEW means Never, Ever Worked)
Bad regulator
Bad pickup sock in tank
Kinked fuel hose at tank or pump.
Bad pump (I know, its new. But sometimes NEW means Never, Ever Worked)
Bad regulator
08-27-2007, 09:23 AM
#15
Drifting
Thread Starter
What would be the most likley considering it happens as the care warms up and runs?
