fuel
Thread Starter
Heel & Toe
Joined: Jan 2011
Posts: 17
Likes: 0
fuel
hey my 86 wont start i turn the key on, and my gauge on the fuel rail jumps to 40 then zero i replaced the presssure regulator,fuel pump,injectors and deleted the ninth injector . what could be the problem
Race Director
Joined: May 2006
Posts: 10,691
Likes: 71
From: Phoenix Arizona
Since you are not reporting any external gas leaks, the problem is probably in the gas tank (you've changed everything else). You're probably losing pressure at the damper between the fuel pump and the hard line. It's a poor design and later they discontinued it. Replace it with a piece of gas line. There is a chance it could be a defective fuel pump also. If that fails, plug the line at the fuel filter and see if you maintain pressure.
Last edited by zr1fred; Jan 23, 2011 at 12:46 PM.
Team Owner
Joined: Jan 2009
Posts: 73,568
Likes: 33
From: Somewhere in Mo
St. Jude Donor '09-'10, '14
Did you replace the FPR or the diaphragm?
The new after market made in Mexico Diaphragms do not like to seat properly on the original housing for whatever reason.
Been through this already as has others. The only fix I've read is to replace the whole unit, there was one fix that requires sanding of the pintle on the diaphragm that worked for a member.
But this is considering everything else checks out as has been suggested. But if you're getting fuel it should start unless it's a spark issue. The fuel filter shouldn't be the problem if it jumps to 40 and then drops back. That tells me the filter isn't resrticting fuel. But i could be wrong.
The new after market made in Mexico Diaphragms do not like to seat properly on the original housing for whatever reason.
Been through this already as has others. The only fix I've read is to replace the whole unit, there was one fix that requires sanding of the pintle on the diaphragm that worked for a member.
But this is considering everything else checks out as has been suggested. But if you're getting fuel it should start unless it's a spark issue. The fuel filter shouldn't be the problem if it jumps to 40 and then drops back. That tells me the filter isn't resrticting fuel. But i could be wrong.
Last edited by RetiredSFC 97; Jan 23, 2011 at 01:04 PM.
Thread Starter
Heel & Toe
Joined: Jan 2011
Posts: 17
Likes: 0
fuel
Since you are not reporting any external gas leaks, the problem is probably in the gas tank (you've changed everything else). You're probably losing pressure at the damper between the fuel pump and the hard line. It's a poor design and later they discontinued it. Replace it with a piece of gas line. There is a chance it could be a defective fuel pump also. If that fails, plug the line at the fuel filter and see if you maintain pressure.
Thread Starter
Heel & Toe
Joined: Jan 2011
Posts: 17
Likes: 0
fuel
Did you replace the FPR or the diaphragm?
The new after market made in Mexico Diaphragms do not like to seat properly on the original housing for whatever reason.
Been through this already as has others. The only fix I've read is to replace the whole unit, there was one fix that requires sanding of the pintle on the diaphragm that worked for a member.
But this is considering everything else checks out as has been suggested. But if you're getting fuel it should start unless it's a spark issue. The fuel filter shouldn't be the problem if it jumps to 40 and then drops back. That tells me the filter isn't resrticting fuel. But i could be wrong.
The new after market made in Mexico Diaphragms do not like to seat properly on the original housing for whatever reason.
Been through this already as has others. The only fix I've read is to replace the whole unit, there was one fix that requires sanding of the pintle on the diaphragm that worked for a member.
But this is considering everything else checks out as has been suggested. But if you're getting fuel it should start unless it's a spark issue. The fuel filter shouldn't be the problem if it jumps to 40 and then drops back. That tells me the filter isn't resrticting fuel. But i could be wrong.
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Race Director
Joined: May 2006
Posts: 10,691
Likes: 71
From: Phoenix Arizona
If the fuel pressure is dropping rapidly to zero, you have a pressure loss somewhere in the system. It has to be the pump, line, regulator, or injectors. Just because you've already changed something doesn't necessarily mean it isn't the problem. Sometimes you get bad parts. I've had problems with the above mentioned damper, which I've had, or as in the case of my pickup, the line in the fuel tank split. Once you've reached 40lbs, it shouldn't drop (a small drop is normal say 10%) untill you start the engine.
Thread Starter
Heel & Toe
Joined: Jan 2011
Posts: 17
Likes: 0
If the fuel pressure is dropping rapidly to zero, you have a pressure loss somewhere in the system. It has to be the pump, line, regulator, or injectors. Just because you've already changed something doesn't necessarily mean it isn't the problem. Sometimes you get bad parts. I've had problems with the above mentioned damper, which I've had, or as in the case of my pickup, the line in the fuel tank split. Once you've reached 40lbs, it shouldn't drop (a small drop is normal say 10%) untill you start the engine.