Switching back from propane need help!
Thread Starter
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Fleet Mechanic
Joined: Jan 2012
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From: Saskatchewan
Switching back from propane need help!
Well like the title says I'm switching a 88 bronco back to gas from propane. It's been a challenge. So far I've replaced the fuel tank, sender and in tank pump because the old parts were way to rusty to put back in. They unplugged the inertia switch and all the injectors which I've since reconnected. I can hear the fuel pump run for a couple seconds when I turn the key on but it still won't fire. It ran fine on propane and it runs if I spray carb cleaner in the throttle body but it won't take off. There is fuel pressure at the fuel rail, enough to spray out when I press the schreder valve but I don't have a proper gauge to tell the exact pressure. I'm thinking maybe the injectors aren't pulsing but thought I would consult with the experts here. Lol. Any ideas? Thanks in advance.
Lead Driver
Joined: May 2011
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its pretty typical for the injectors to be stuck when going from propane back to gas. might be a good idea to pull the intake and check out the injectors....or keep it running on ether/carb cleaner for a while and see if they free up.
Thread Starter
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
Ah crap I already had it off to plug in all the injectors. Lol. So what should I be looking at when I remove them? Do they come apart? Thanks
Lead Driver
Joined: May 2011
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Have to pop the fuel rail off after you get the intake off.
You can see if the fuel injectors are firing on the drivers side, which is accessible, by using a voltmeter while running (cranking) or putting 12v to the injector itself and see if you can hear or feel it moving.
Curious, I'm assuming the distributor is factory?
You can see if the fuel injectors are firing on the drivers side, which is accessible, by using a voltmeter while running (cranking) or putting 12v to the injector itself and see if you can hear or feel it moving.
Curious, I'm assuming the distributor is factory?
Thread Starter
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
Have to pop the fuel rail off after you get the intake off.
You can see if the fuel injectors are firing on the drivers side, which is accessible, by using a voltmeter while running (cranking) or putting 12v to the injector itself and see if you can hear or feel it moving.
Curious, I'm assuming the distributor is factory?
You can see if the fuel injectors are firing on the drivers side, which is accessible, by using a voltmeter while running (cranking) or putting 12v to the injector itself and see if you can hear or feel it moving.
Curious, I'm assuming the distributor is factory?
Thread Starter
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
Well I'm stumped. Lol. I pulled all the injectors out and cleaned them. Also applied 9volts to them and they all click. I also put my test light on one of the injectors while cranking and its flashing. I wonder if I have enough fuel pressure. I can hear the main pump running but maybe it's no good. I'll have to find a gauge and see what I got. Ideas are welcome. Thanks
Lead Driver
Joined: Aug 2006
Posts: 5,670
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From: Sand Lake, MI
Well I'm stumped. Lol. I pulled all the injectors out and cleaned them. Also applied 9volts to them and they all click. I also put my test light on one of the injectors while cranking and its flashing. I wonder if I have enough fuel pressure. I can hear the main pump running but maybe it's no good. I'll have to find a gauge and see what I got. Ideas are welcome. Thanks
And yes a fuel pressure test would be a good idea briefly flow tested those injectors or not.
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Lead Driver
Joined: Jul 2007
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From: Rhode Island
Also, make sure the fuel in the rail is actually good, too. If the truck had been sitting with bad fuel in the lines forever, it might take a bit for it to cycle out.
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Lead Driver
Joined: May 2011
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If you've ever seen a gummed up carb from gas evaporating, you'll know it can get pretty damn cruddy.
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Fleet Mechanic
Joined: Jan 2012
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From: Saskatchewan
Did alittle more poking around and checked the fuel pressure. It's about 37psi when I first turn the key on and climbs up to 40psi cranking but bleeds down quickly as soon as the key is shut off. That would mean a injector is stuck in the open position I'm thinking. Im going to pump some new fuel through the rail by removing the schrader valve and see how it looks but when I had the rail off the fuel that was spilled out seemed fresh but I'd rather cover all the bases before shelling out $$ for new injectors. Thanks again for the help.
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
Did alittle more poking around and checked the fuel pressure. It's about 37psi when I first turn the key on and climbs up to 40psi cranking but bleeds down quickly as soon as the key is shut off. That would mean a injector is stuck in the open position I'm thinking. Im going to pump some new fuel through the rail by removing the schrader valve and see how it looks but when I had the rail off the fuel that was spilled out seemed fresh but I'd rather cover all the bases before shelling out $$ for new injectors. Thanks again for the help.
Bleeds off quick and might be due to injectors but has adequate fuel pressure to run with power to the pump.
Test you could do to narrow down where but couple questions.
Have you pulled all the plugs to see if any of them show signs of fuel?
Does the fuel pressure increase when you remove the vac line to the FPR? (engine running at idle of course)
Didn't see where you mentioned doing anything with the FPR after changing back to gasoline, it might be fine but might be stuck/gummed up.
Thread Starter
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
Bleeds off quick and might be due to injectors but has adequate fuel pressure to run with power to the pump.
Test you could do to narrow down where but couple questions.
Have you pulled all the plugs to see if any of them show signs of fuel?
Does the fuel pressure increase when you remove the vac line to the FPR? (engine running at idle of course)
Didn't see where you mentioned doing anything with the FPR after changing back to gasoline, it might be fine but might be stuck/gummed up.
Test you could do to narrow down where but couple questions.
Have you pulled all the plugs to see if any of them show signs of fuel?
Does the fuel pressure increase when you remove the vac line to the FPR? (engine running at idle of course)
Didn't see where you mentioned doing anything with the FPR after changing back to gasoline, it might be fine but might be stuck/gummed up.
Thread Starter
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
I pulled the schrader valve and pumped what looks to me like brand new fuel into a jug. Prolly about 2liters. Should be more than enough to flush out the old lines. So at this point if I have 40psi of good fuel to my injectors and the computer if trying to fire them it pretty much hast to be the injectors right? Lol
And lastly what are my injector options? Prolly new or remans? Are the rebuilt ones junk? Thanks everybody.
And lastly what are my injector options? Prolly new or remans? Are the rebuilt ones junk? Thanks everybody.
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
I pulled the plugs once and they were all dry at that point before I cleaned the injectors. Hard to tell if the pressure regulator is working since I can't get it to idle. Seems to me that 40psi should be enough pressure to atomize the fuel if the injectors were working properly.
It would default to highest pressure value as no vacuum present at the FPR required to reduce it.
There is a couple tests you can do to eliminate the FPR and the check valve in the supply line side if you wish to do so before tearing into it again, but it has plenty of fuel pressure while the pump is running to start and run, pressure bleeds off quickly key "off" or not..
Thread Starter
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Fleet Mechanic
Joined: Jan 2012
Posts: 1,668
Likes: 13
From: Saskatchewan
Sounds like the injectors still need work, checking the fuel pressure by removing the vac line if it didn't run of course wouldn't be possible.
It would default to highest pressure value as no vacuum present at the FPR required to reduce it.
There is a couple tests you can do to eliminate the FPR and the check valve in the supply line side if you wish to do so before tearing into it again, but it has plenty of fuel pressure while the pump is running to start and run, pressure bleeds off quickly key "off" or not..
It would default to highest pressure value as no vacuum present at the FPR required to reduce it.
There is a couple tests you can do to eliminate the FPR and the check valve in the supply line side if you wish to do so before tearing into it again, but it has plenty of fuel pressure while the pump is running to start and run, pressure bleeds off quickly key "off" or not..