engine won't stay on

[SaltyMKIII]

hey guys i had to swap a 7mge into my car. the ECU and wiring harness is for a auto tranny,my car was originally a turbo 5sp but i blew my motor, so to keep my car on the road while im rebuilding my 7mgte i did that swap. the engine starts but it wont stay on. if you start the car and open the throttle slightly the car cut out, but if you give it wot it'll run for 20 seconds or so then shuts off. im reading in the manual tonight and going to keep troubleshooting tomorrow. If any one has dealt with a similar problem any input would be helpful,

thanks

 

[hvyman]

Any codes?

 

[SaltyMKIII]

im gonna look those up in the morning. the engine ran 5 days ago while it was in the other car, butt would run only when i gave it gas. when i took my foot off the peddle the car would stall so im kinda thinking it might be the ISC valve

 

[ifyouaint1sturlast]

Soooo what harness and everything are you running?

 

[SaltyMKIII]

its a 7mge auto harness/ ecu, with a R154, i rewired the harness to work with a manual trans.

 

[ifyouaint1sturlast]

I would certainly say check for codes.

 

[SaltyMKIII]

No codes I checked them this morning. The ISC valve is good, I'm checking for vacuum leaks then im gonna troubleshoot the ecu to see if that working right , the fuel pump works... Does anyone have any other ideas?

 

[ifyouaint1sturlast]

Check fuel pressure

 

[SaltyMKIII]

It's a walbro and its putting out 48

 

[ifyouaint1sturlast]

Check fuel pressure at the time the engine dies..

 

[hvyman]

48 psi at the rail?

 

[SaltyMKIII]

It not that I had my dad play with the throttle body right after I started it and he kept it running around 2000 rpm then it would die if he went above 2500 and below 1800 so I'm looking into the thottlebody and the tbp sensor

 

[SaltyMKIII]

Yea its 48 at the rail the book says 38-44 for the NA, and after I shut off the pump it held the pressure past the stated time. The TPS for both 7MGTE and 7MGE are the same right?

 

[SaltyMKIII]

Check fuel pressure at the time the engine dies..

I had to install my aero fpr so I could check the pressure as the the engine stalls. But I dropped one of the fittings and it fell in this one little spot where I couldn't get to, I had to take the starter off just to get me bear paws in tgere. Anyway after I set everything up set the fpr to 40 then started the car and samethis but the fuel pump shuts down then the engine stalls. So I jumped out the efi relay to keep the pump on and bingo the cat runs. Now its time to go get a new relay .

Thanks for asking the right question I do appropriate the help

 

[ifyouaint1sturlast]

I had to install my aero fpr so I could check the pressure as the the engine stalls. But I dropped one of the fittings and it fell in this one little spot where I couldn't get to, I had to take the starter off just to get me bear paws in tgere. Anyway after I set everything up set the fpr to 40 then started the car and samethis but the fuel pump shuts down then the engine stalls. So I jumped out the efi relay to keep the pump on and bingo the cat runs. Now its time to go get a new relay .

Thanks for asking the right question I do appropriate the help

I had a feeling the fuel pump was dying. It may not be the relay though, it may be what's triggering the relay. I've seen it on 1JZ swaps a lot. Glad I could help!

 

[SaltyMKIII]

Ok I'll trace it out tomorrow, I have the electrical schematic so I'll see where the fault is.

 

[SaltyMKIII]

after checking every component in the EFI circuit, all i could determine that all the components were good. so i made a bunch of extension with a line spliced in the middle so i could see whats going on my my fluke meter, looking in the electrical diagram you can trace out the flow of electricity and start jumping out components until you find out were the fault is. i found out that the "open circuit relay" was staying closed so the fuel pump wasnt staying on. i jumped out the relay in the air flow meter to see in that did it and bingo there was a open somewhere in between the airflow meter and ground. after finding the other end of the wire i found out the the NA wiring harness had a discrepancy with my turbo body harness, so i soldered in a new ground on the engines wiring harness cause i didnt want to undo any electrical changes later when i put my 7mgte back in.