Need help before I scrap her....
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Joined: Apr 2013
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Need help before I scrap her....
1990 F150 4.9 4x4 87,000 original miles
I've done EVERYTHING under the sun to get this beast to start. It was running fine and one morning I went out and it just turned over and would not start. No codes are being thrown. I have 35lbs of pressure on the fuel rail with key on. 12v to pump. Truck starts briefly with starting fluid in the intake.
Here's what I've done:
Replaced both fuel pumps(there are only 2)
Replaced fuel filter (there is only 1)
Replaced fuel selector valve
Replaced fuel selector on dash
Replaced all relays
Replaced battery and cables
Replaced fuel lines and vacuum lines
Replaced fuel pressure regulator
Replaced spark plugs
Replaced PCM
Probably a few more things I'm forgetting
I've had no less than 10 "mechanics" try to diagnose this thing. All of the above were done at their request. None of these things fixed or changed the problem. Next stop is the scrap yard if I can't get it running soon.
ANY help would be appreciated
I've done EVERYTHING under the sun to get this beast to start. It was running fine and one morning I went out and it just turned over and would not start. No codes are being thrown. I have 35lbs of pressure on the fuel rail with key on. 12v to pump. Truck starts briefly with starting fluid in the intake.
Here's what I've done:
Replaced both fuel pumps(there are only 2)
Replaced fuel filter (there is only 1)
Replaced fuel selector valve
Replaced fuel selector on dash
Replaced all relays
Replaced battery and cables
Replaced fuel lines and vacuum lines
Replaced fuel pressure regulator
Replaced spark plugs
Replaced PCM
Probably a few more things I'm forgetting
I've had no less than 10 "mechanics" try to diagnose this thing. All of the above were done at their request. None of these things fixed or changed the problem. Next stop is the scrap yard if I can't get it running soon.
ANY help would be appreciated
Logistics Pro
Joined: Mar 2012
Posts: 3,507
Likes: 121
From: Oregon
Have you tested the ignition control module mounted on the distributor? They tend to go bad due to heat failure from being mounted on the distributor. That is why Ford switched to a remote mounted on on the 92+ trucks.
Logistics Pro
Joined: Mar 2012
Posts: 3,507
Likes: 121
From: Oregon
If that's the case it sounds like a fuel delivery issue. Since almost all of the fuel system is new, I would suspect something with the injectors not firing. I believe that still leaves the ICM as a possible fault.
Posting Guru
Joined: May 2010
Posts: 1,146
Likes: 17
From: Central Indiana
Hmm . . .
When you replaced the PCM, was it new/rebuilt/loaned/pick-yer-part? I always taught my students to go with the adage, 'Just because it's new, doesn't mean it works'. PCM could still be bad.
Have you tested the injector ckts to see that you're getting power to the injectors when you crank the engine? A noid light would tell you that. Common 12V B+ to the injectors, each injector is fired by the PCM grounding the individual injector or in the case of Speed Density, firing the entire bank.
Just my thoughts,
Ray
Have you tested the injector ckts to see that you're getting power to the injectors when you crank the engine? A noid light would tell you that. Common 12V B+ to the injectors, each injector is fired by the PCM grounding the individual injector or in the case of Speed Density, firing the entire bank.
Just my thoughts,
Ray
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New User
Joined: Apr 2013
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Thanks for all the replies. I'll check these things and report back.
The PCM was used. I don't think new ones are available. It still could be the problem. I can't even count the number of times I've bought new faulty parts.
I'm located just north of Pittsburgh.
The PCM was used. I don't think new ones are available. It still could be the problem. I can't even count the number of times I've bought new faulty parts.
I'm located just north of Pittsburgh.
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Senior User
Joined: Nov 2002
Posts: 305
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From: Somewhere West of Laramie
Have you tried a known to be good coil? For some reason over the years I've had problems with 3 coils being bad intermittently,drove me nuts each time.
And they always tested good with an ohm meter
And they always tested good with an ohm meter
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The 4.9 needs higher fuel pressure.
I believe the spec is 55 to 60lbs.
The pumps are the same, but the 4.9 uses a different regulator.
Since you used the shotgun approach to repairing this its difficult to say what the problem is.
If the regulator is new I'd check its part number online on the website for the store where you got it and see if it is the one for a 4.9.
If its not new I would check the fuel pressure with your guage before it reaches the fuel rail, at the filter is prob the easiest. If the pressure there is higher than the spec I would go buy the right regulator.
I believe the spec is 55 to 60lbs.
The pumps are the same, but the 4.9 uses a different regulator.
Since you used the shotgun approach to repairing this its difficult to say what the problem is.
If the regulator is new I'd check its part number online on the website for the store where you got it and see if it is the one for a 4.9.
If its not new I would check the fuel pressure with your guage before it reaches the fuel rail, at the filter is prob the easiest. If the pressure there is higher than the spec I would go buy the right regulator.
Tuned
Joined: Oct 2012
Posts: 440
Likes: 8
Sounds like a PIP problem to me. Go to Autozone and rent a noid light set. Pull an injector plug and plug the proper noid light into the harness and have someone turn it over. If it doesn't pulse a light, you have either a PIP problem or a computer problem. The PIP is the pick up in the distributor that tells the computer when to pulse the injectors. You can have all the fuel in the world but as long as your injectors aren't squirting that fuel out, you'll never get it to run. Also, I'm pretty sure you should be getting a code 11 (or maybe it's 111?) for "System Pass" as long as there's no other codes. If you're not getting any codes at all, that may be a sign of a bad computer.
Postmaster
Joined: Nov 2011
Posts: 3,533
Likes: 17
From: SW Florida
Sounds like a PIP problem to me. Go to Autozone and rent a noid light set. Pull an injector plug and plug the proper noid light into the harness and have someone turn it over. If it doesn't pulse a light, you have either a PIP problem or a computer problem. The PIP is the pick up in the distributor that tells the computer when to pulse the injectors. You can have all the fuel in the world but as long as your injectors aren't squirting that fuel out, you'll never get it to run. Also, I'm pretty sure you should be getting a code 11 (or maybe it's 111?) for "System Pass" as long as there's no other codes. If you're not getting any codes at all, that may be a sign of a bad computer.
The Southernmost Mod
Joined: Dec 2004
Posts: 6,902
Likes: 20
From: Caracas, Venezuela
Since shooting ether makes it start briefly I would be searching for a fuel related issue, the fuel pressure should be around 39-40 psi for the V8s, not sure about the I6, if it's 60 psi then this surely is the cause. The other possible cause I can think of is the TFI, which controls both the spark and the signal for the injectors.
Post Fiend
Joined: Oct 2003
Posts: 9,176
Likes: 4
From: Western Central NV
The 4.9 needs higher fuel pressure.
I believe the spec is 55 to 60lbs.
The pumps are the same, but the 4.9 uses a different regulator.
Since you used the shotgun approach to repairing this its difficult to say what the problem is.
If the regulator is new I'd check its part number online on the website for the store where you got it and see if it is the one for a 4.9.
If its not new I would check the fuel pressure with your guage before it reaches the fuel rail, at the filter is prob the easiest. If the pressure there is higher than the spec I would go buy the right regulator.
I believe the spec is 55 to 60lbs.
The pumps are the same, but the 4.9 uses a different regulator.
Since you used the shotgun approach to repairing this its difficult to say what the problem is.
If the regulator is new I'd check its part number online on the website for the store where you got it and see if it is the one for a 4.9.
If its not new I would check the fuel pressure with your guage before it reaches the fuel rail, at the filter is prob the easiest. If the pressure there is higher than the spec I would go buy the right regulator.
Sounds like a PIP problem to me. Go to Autozone and rent a noid light set. Pull an injector plug and plug the proper noid light into the harness and have someone turn it over. If it doesn't pulse a light, you have either a PIP problem or a computer problem. The PIP is the pick up in the distributor that tells the computer when to pulse the injectors. You can have all the fuel in the world but as long as your injectors aren't squirting that fuel out, you'll never get it to run. Also, I'm pretty sure you should be getting a code 11 (or maybe it's 111?) for "System Pass" as long as there's no other codes. If you're not getting any codes at all, that may be a sign of a bad computer.
My question is why didn't one of these 10 mechanic fix the problem? It would of been way cheaper to of taken this to a shop & had it fixed. Sure would of saved a lot of parts changing. Which is as a rule the most expensive way to fix a vehicle.
Craig
Senior User
Joined: May 2010
Posts: 285
Likes: 0
Truck may have more than one problem, who knows?
The one thing we do know from the information given is that the fuel pressure is not correct.
Kind of pointless to test, find something wrong, and then ignore it and work on something else isn't it?
The one thing we do know from the information given is that the fuel pressure is not correct.
Kind of pointless to test, find something wrong, and then ignore it and work on something else isn't it?