Fuel Pressure?
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
Yeah, unhooking the battery for at least 10 minutes will drain the computer's internal memory, causing it go back to the base map, and "relearn" the paramaters that work best for the individual vehicle.
Works on OBD-I and OBD-II systems. Of course, the fancier OBD-II scanners have not only a code erase feature, but also a full reset option that eliminates the need to unhook the battery. OBD-I was a bit less advanced.......
Works on OBD-I and OBD-II systems. Of course, the fancier OBD-II scanners have not only a code erase feature, but also a full reset option that eliminates the need to unhook the battery. OBD-I was a bit less advanced.......
Post Fiend
Joined: Jul 2004
Posts: 8,786
Likes: 28
From: Northern California
I agree with RW, It sounds like he needs a new selector valve for his dual tanks. If he's going to delete the rear tank, then he doesn't need it in the system. That selector valve isn't cheap either.
You can also reset the computer using the code scanner with the ignition switch in run. turn the scanner on and off with the ignition switch in run after the KOEO key on engine off, test and it will reset the computer. You should be able to hear it reset. This will also erase all the old codes. Then run the codes again. You may have to drive it for a spell for it to pick up new codes if there is an intermittent problem.
You can also reset the computer using the code scanner with the ignition switch in run. turn the scanner on and off with the ignition switch in run after the KOEO key on engine off, test and it will reset the computer. You should be able to hear it reset. This will also erase all the old codes. Then run the codes again. You may have to drive it for a spell for it to pick up new codes if there is an intermittent problem.
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
I don't think my scanner has an on/off switch. It turns on when you plug it in, and off when you unplug it. It has 2 switches, one for audio on/off, and one marked test/hold.
Ray's truck was the first time I ever saw it in action, as I just found it in dad's truck. He told me to keep it, and track down the rest of his lifetime's accumulation of tools, and keep those too......
Ray's truck was the first time I ever saw it in action, as I just found it in dad's truck. He told me to keep it, and track down the rest of his lifetime's accumulation of tools, and keep those too......
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
Doesn't surprise me it's an older model, dad did make a living working on these things.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Sounds like you guys have just about solved the issues though, the fuel system on these older trucks was a convoluted mess. They did away with it in 1990 and went to a system that simply had a fuel delivery module inside each tank with a couple check valves to prevent backfilling when the other tank is in use and a high pressure pump, externally there is nothing between the tanks and engine except a fuel filter.
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
The "warm up" time on the O2 sensor also partly explains the switch to a heated O2 sensor in the later models.
Kinda sounds like Ray was on the right track from the start, since the thread is titled "Fuel Pressure", which turned out to be a major factor. Might not be the only one, but certainly the most prominent......
Kinda sounds like Ray was on the right track from the start, since the thread is titled "Fuel Pressure", which turned out to be a major factor. Might not be the only one, but certainly the most prominent......
Post Fiend
Joined: Jul 2004
Posts: 8,786
Likes: 28
From: Northern California
Well actually no it can't because in cold start mode the computer also ignores the O2 sensor.. which is just as well because it too needs a little time to warm up. The trigger to switch from cold start open loop to closed loop is on engine coolant temperature.. somewhere around 160deg or so, so in many cases you're actually driving away before closed loop happens.
How does the computer know that the thermactor system is disconnected and to throw a code 44? I know it uses the O2 sensor to sense the switching. There are also Code 45 for air always upstream or defective TAD solenoid and Code 46 for air not bypassing or defective TAB solenoid. Also why would the computer put the code 44 on the highest prioity, when I would think the IAC code is more important to check on?
From what I gather you are stating that the computer shouldn't realise there is a problem with the thermactor system, so how is it finding out?
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Post Fiend
Joined: Jul 2004
Posts: 8,786
Likes: 28
From: Northern California
Will be interested in finding out what the computer says now.
Thread Starter
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Laughing Gas
Joined: Feb 2011
Posts: 1,147
Likes: 6
From: Vine Grove KY
After all this I would still like to just rip all this efi crap off and slap on a carb....but I will get this working first and see how things go. If I get another vehicle like a civic or something for daily driving I might just switch this truck over to a carb....I know how to tune those blind folder by sound and smell with a screw driver...this EFI Crap is over rated and over complicated if you ask me. Im with RW, I guess I am just old school (even though I am only 25yrs old)
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
Don't think I posted the pic of the Edelbrock 302 manifold from last evening's "find". I did post the pic of the carb, but I think I want it. However, not sure I can stretch the manifold enough to fit, and hear that RTV won't stand up to gas. 
Having said that, I think you'll like the EFI when it really is working.
Having said that, I think you'll like the EFI when it really is working.
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
After all this I would still like to just rip all this efi crap off and slap on a carb....but I will get this working first and see how things go. If I get another vehicle like a civic or something for daily driving I might just switch this truck over to a carb....I know how to tune those blind folder by sound and smell with a screw driver...this EFI Crap is over rated and over complicated if you ask me. Im with RW, I guess I am just old school (even though I am only 25yrs old)
EFI is great in many ways. But, much like all the fancy electronic gizmo's on newer vehicles, it's just more stuff to go wrong, and takes far more complex tools to diagnose and correct.
I feel much the same way newer diesel's. Mechanical injection has it's limitations, but the reliability is unmatched by today's "modern" diesel's with computer controlled direct injection and multi-shot common rail injection systems.
Post Fiend
Joined: Jul 2004
Posts: 8,786
Likes: 28
From: Northern California
After all this I would still like to just rip all this efi crap off and slap on a carb....but I will get this working first and see how things go. If I get another vehicle like a civic or something for daily driving I might just switch this truck over to a carb....I know how to tune those blind folder by sound and smell with a screw driver...this EFI Crap is over rated and over complicated if you ask me. Im with RW, I guess I am just old school (even though I am only 25yrs old)
Being EFI it's more tricky...
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
Don't think I posted the pic of the Edelbrock 302 manifold from last evening's "find". I did post the pic of the carb, but I think I want it. However, not sure I can stretch the manifold enough to fit, and hear that RTV won't stand up to gas.
Having said that, I think you'll like the EFI when it really is working.
Having said that, I think you'll like the EFI when it really is working.
Yeah, I don't think that 302 intake will work very well on a 351W, since I can't find that "intake stretcher" that is rumored to exist for putting a 351C 4V intake on a 400.......
Seriously, the 351C intake *can* be used on a 351M/400, but it requires spacers that go between the intake and heads. They cost more than an aftermarket intake these days.
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