whistlin'
01-04-2007, 07:42 PM
Working on a friend's 89 conversion van w/5.9L TBI. First I'll give the symptoms. The van runs great and starts good when cold. After driving around for awhile then park it and shut off, it has trouble starting. If starting it immediately after shutting off, it starts fine. 20 minutes after shutting off, it takes a lot of cranking to start. 1 hour after shutting off, it starts fine. If it was carburetted I would say the symptoms are like boiling over. He took it to a shop and they told him it was the fuel pump. I changed the pump for him even though I didn't think it was bad. My first thought was a leaky injector. I shut it off and looked down the throttle body and didn't see any fuel leaking.
I then checked fuel pressure. 15-17psi. Funny thing is, as soon as I shut it off the pressure dropped to 0. I pinched off the return line and tried again, 17 psi until shutting off then 0. I took the van for a drive with the dog house off and watched the pressure, stayed right at 17 regardless of driving technique. I disconnected the vacuum line to the regulator, no change. I would assume the regulator was bad but I couldn't feel any vacuum from the line going to the regulator.
When I returned home I connected a vacuum line to the regulator and applied vacuum(sucked):lol: The pressure then dropped to about 5 psi, I could just about shut the motor off by doing this.
So.... is the vacuum line going to the regulator supposed to provide manifold vacuum? If so, any reasons why this one isn't?
And does the fuel pump have a bypass built into it? Wondering why I didn't get a pressure spike when pinching return line. Any help would be appreciated.
I then checked fuel pressure. 15-17psi. Funny thing is, as soon as I shut it off the pressure dropped to 0. I pinched off the return line and tried again, 17 psi until shutting off then 0. I took the van for a drive with the dog house off and watched the pressure, stayed right at 17 regardless of driving technique. I disconnected the vacuum line to the regulator, no change. I would assume the regulator was bad but I couldn't feel any vacuum from the line going to the regulator.
When I returned home I connected a vacuum line to the regulator and applied vacuum(sucked):lol: The pressure then dropped to about 5 psi, I could just about shut the motor off by doing this.
So.... is the vacuum line going to the regulator supposed to provide manifold vacuum? If so, any reasons why this one isn't?
And does the fuel pump have a bypass built into it? Wondering why I didn't get a pressure spike when pinching return line. Any help would be appreciated.