nelstomlinson
Full Access Member
First the story, then a couple of questions at the bottom.
Friday my truck started surging then died on the way home. I told a little about it in the what did you do with your truck today thread.
This truck is my '89 crewcab. It has a small electric fuel pump on the frame rail between the fuel selector switch and the mechanical fuel pump. It also has a check valve in there, before the mechanical fuel pump. I believe everything else is stock, except that I have deleted the return line which connected to the fuel filter.
When I investigated, I found that the filter on the input of the electric pump was NOT clogged. I found a crack in the hose leading out of the pump, with a drip when the e-pump was running. I changed that bit of hose, and got it restarted, and now it's better, it runs again, but it's still not right.
What it's doing now is it drives OK, with barely noticeable surging at higher RPMs, but will surge noticeably at idle, or when downshifting. There is some hesitation on acceleration, too. I keep getting air out of the schraeder valve when it's not running. I haven't tried bleeding it while running yet.
So far I have changed that bit of fuel line, have checked that the e-pump filter isn't clogged, have changed the main fuel filter and used the e-pump to bleed the air out of it, can't find any more leaks.
Is it possible that the mechanical fuel pump is somehow partially failing, and can't pump enough fuel at low RPMs, and barely enough at high RPMs? Could it be sucking air somehow but not leaking? I have checked the lube oil level, and it hasn't gotten higher. I'm sort of at a loss for what to try next, would appreciate hints or ideas.
Friday my truck started surging then died on the way home. I told a little about it in the what did you do with your truck today thread.
This truck is my '89 crewcab. It has a small electric fuel pump on the frame rail between the fuel selector switch and the mechanical fuel pump. It also has a check valve in there, before the mechanical fuel pump. I believe everything else is stock, except that I have deleted the return line which connected to the fuel filter.
When I investigated, I found that the filter on the input of the electric pump was NOT clogged. I found a crack in the hose leading out of the pump, with a drip when the e-pump was running. I changed that bit of hose, and got it restarted, and now it's better, it runs again, but it's still not right.
What it's doing now is it drives OK, with barely noticeable surging at higher RPMs, but will surge noticeably at idle, or when downshifting. There is some hesitation on acceleration, too. I keep getting air out of the schraeder valve when it's not running. I haven't tried bleeding it while running yet.
So far I have changed that bit of fuel line, have checked that the e-pump filter isn't clogged, have changed the main fuel filter and used the e-pump to bleed the air out of it, can't find any more leaks.
Is it possible that the mechanical fuel pump is somehow partially failing, and can't pump enough fuel at low RPMs, and barely enough at high RPMs? Could it be sucking air somehow but not leaking? I have checked the lube oil level, and it hasn't gotten higher. I'm sort of at a loss for what to try next, would appreciate hints or ideas.