guys i realy realy dont know what the heck is going on.. Fuel (or something problem)

[F 150Cobra]

im having this trouble
i hoe you guys dont mind that i post this link here.


but the strange thing is once you get it started it can run allday long without any problems..

help! please!!!!!!!! im confused..

thank you the one who solves my problem will get an carbed 460 lol !!!

 

[O'Rattlecan]

hopefully vince or one of the techs will be along shortly.

You may want to double post in another section just to make sure other members may have a chance to see it.

Ryan

 

[Skandocious]

hopefully vince or one of the techs will be along shortly.

You may want to double post in another section just to make sure other members may have a chance to see it.

Ryan

Everyone read that post a few times and savor the flavor. I do believe its the first and last time you'll ever see an admin SUGGEST one of the user's to double post!!

 

[blacksnapon]

You've already discovered the problem. Remember us suggesting that you check fuel pressure? Your post that said the pressure bleeds off when you turn off the key,points you in a particular direction. It should hold pressure for three minutes at least. You need to find the reason why. Possible reasons: injectors leaking, fuel line leaks, fuel pressure regulator, fuel pump, or check valve. Now is the time to start looking. We can't do anything on the internet that you need to do to repair it.

 

[F 150Cobra]

regulator and fuel pump has been changed... how to see if the injectors are leaking?
and what chek valve? where?


BTW im going to do a dubbel chek fuel pressure test.. how many psi should it hold for how long?

 

[bowtiehatr]

35 psi is spec. you also have a selector switch that could be hanging causing the issue, which means if you replaced 1 pump you might also need to replace the other pump along with the selector switch.

does the truck run rough when you start it? if not more than likely you have a check valve issue.

 

[F 150Cobra]

yes it does run rough when i start it if i dont let it finish priming.. it wil run rough with black smoke and with chek engine light on and will stop somethimes if i press the brakes or let it idle a while... strange eh ?


but where is the chek valve?

 

[F 150Cobra]

i found this it has the SAME EXACT symptom of mine.. so i guess i need a new computer... but now where to get one... ?? how much ? $$$

vehicle info for computer

1990 351W
E40D

 

[bowtiehatr]

you need to diagnose the issue before you throw parts at it.

 

[mrfixit]

Really need to pull codes if at ALL possible. Replacing that computer gets pricey. This sounds like an Idle Air Controller sticking. Mine did the same thing on my '89 5.8. I pulled it, cleaned the heck out of it and put it back on... worked like a charm.

 

[F 150Cobra]

idle air control is sticking and let the fuel pump primes for about 10 mins? hmmm dont think so

i think its the computer.. becuase it has alot of 30 psi + PSi at rail a second after i switch it on and once in a while it doesnt do it.. any one think its the relay? can a relay stick?

 

[ponyracer]

does it act the same way on both tanks? I am with the other guys wondering about bleed off and suspecting the check valve in one tank or the other. there was a recall for dual tanks a few years back, did you have it done?

 

[F 150Cobra]

dunno we got the truck 3rd hand... i was wondering that to.. but the rear doesnt have a pump in it yet..i have one to put in.. since i put a new one in the front and it was good.. so i dont think its the chek valve..


im 100 % its the computer becuase somethimes it wont even go into 4th and the OD button doesnt work.. and somethimes at WOT.. it will shift at 3800 and not at 4300 where its soppose to be.. so the computer only works when it wants..


im waiting for JAN to order a new one.. if you guys know where i can find a good one good price please letme know

 

[john112deere]

I am no expert on computers, or automatic transmissions, but- is it even the same computer that runs the fuel pump and the transmission?

 

[O'Rattlecan]

Grim, try cleaning out the wire harness that connects to the nuetral safety switch. It's located (on my truck) on the driver side of the transmission.

Ryan

 

[F 150Cobra]

I am no expert on computers, or automatic transmissions, but- is it even the same computer that runs the fuel pump and the transmission?

from what i learned the computer sends the signal to close or open the relay thats in the circuit of the fuel pump becuase the fuel pump relay has a constant 12V to it and another 12V when you swith it on and a ground signal feed by the EEC is soppose to close or open the relay so basicly the computer is not sending the ground to it ,, it does but after 10 minutes or more,


and yes the transmission and torque converter is full electronicly controlled on the E40D

 

[d-kuzmen]

from what i learned the computer sends the signal to close or open the relay thats in the circuit of the fuel pump becuase the fuel pump relay has a constant 12V to it and another 12V when you swith it on and a ground signal feed by the EEC is soppose to close or open the relay so basicly the computer is not sending the ground to it ,, it does but after 10 minutes or more,


and yes the transmission and torque converter is full electronicly controlled on the E40D

Have you tried a different fuel pump relay? Also the EEC relay? If the eec relay sticks off the pcm won't turn on and you'll get no fuel pump either. I would also use a volt meter and put the pos lead to the pos bat post, pull the fuel pump relay out and put the neg lead to relay ground to PCM. Turn key on to see if you get a 12 volt reading on the meter. If it goes voltage goes right up i'd say the pcm is working. If not then I would check the resistance of the ground wire between the fuel pump relay and pcm. If all seems good then I would start checking the wiring from the relay to the tank.

 

[F 150Cobra]

i found an 1989 van E something.. had an 5.8 with an E4OD !! cheked the code on the computer... and it matched PERFECTLY.. so we swapped it.. and now the truck runs SMOOTH!! gr8 !! and no more waiting 30 minites for the fuel pump to stop prime for it to start.. and no more overdrive botton comes on and off when i press the brake..

it runs like a new truck now.. idles so smooth i forgot i have an muffler.. and can finally enjoy my music, no more WOOHOOHOOO HUM in the cabine

next is A/C!

btw is the idle allitle low??


when in D or R it idles 500

when in P or N idles at 650 -700

good numbers?

 

[eco]

btw is the idle allitle low??


when in D or R it idles 500

when in P or N idles at 650 -700

good numbers?

What were your RPMS before?

Your numbers look normal

With the trans in gear (D, R, etc.) there is then a load on the motor where as there was not with the trans in P or N. There should also be less vacuum in the plenum with the trans in gear (vacuum is directly proportional to load). The load on the motor without an increase in throttle position to accompany (an increase in air, fuel) the RPM should drop, just like your motor does.

 

[F 150Cobra]

mine did those before but was 100-200 higher.. idle in gear was 600-700 and not in gear was 800 and was idling realy really rough... now i cant feel the engine moving when its idling..