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740 won't run without starter fluid solved

bigjoe04

New member
Joined
Jan 21, 2022
Faced with a wrecked 1992 240 manual that still ran and a blown up 1992 740 turbo wagon with an autotragic. I decided to slap the entire 240 drive train into 740 sure I would lose the turbo but I would gain a functional car and it would be a manual. The 740 was a microsquirt big turbo project so it didn't have a wiring harness. Which meant I had to install the lh3.1 240 wiring into the 240. Its been a long journey with lots of custom turbobricks style fabrication including a fitting a cable clutch from the 240 a custom shift cage from scrap metal and lots of unnecessary jankyness stemming from my refusal to spend any money on this project. I am nearly there at this point the car runs on starter fluid but not on its own. I can hear the pumps priming when I turn the key removing the return line from the rail results in fuel sprayed around the engine bay so I'm pretty sure the pumps are good. My theories at the moment are the injectors aren't injecting or maybe the gas went bad from sitting for months. Is there a good way to test injectors? Turns out it just didn't have gas
 
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Can you jump the fuel pumps and try to run it? Are you certain you have power to fuel pumps after you prime/crank?

Also, if you've got a NOID light, you can test for power at injector connector.

What is your wiring setup? It sounds like you used the "stand-alone" 240 engine harness. Do you have the correct signals at the 240 firewall connector, as well as the 4(sometimes 6) wire connector under glove box?
 
Can you jump the fuel pumps and try to run it? Are you certain you have power to fuel pumps after you prime/crank?

Also, if you've got a NOID light, you can test for power at injector connector.

What is your wiring setup? It sounds like you used the "stand-alone" 240 engine harness. Do you have the correct signals at the 240 firewall connector, as well as the 4(sometimes 6) wire connector under glove box?
I'll try jumping the fuel pumps I have them hooked up to the 240 fuel relay right. Yeah I basically created a standalone lh3.1 system there probably aren't to many lh3.1 740s. Im powering the system though the under dash connector Im pretty sure I got it right. Can I test the injector using a normal test light?
 
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Open the cover on the fuel pump relay and confirm both contacts close. One is for EFI and the other contact powers the pumps.
 
Friend of mine has been troubleshooting a similar issue with a 240 sedan lately. Does lh3.1 have that blade fuse under the hood for the fuel system? I don't have a photo of my own but I found this one.


fuse847.jpg
 
Do you have fuel injector pulse?

Do you have fuel pressure?
I just removed the fuel rail and injectors it was injecting on all 4 when cranking confirming pressure and pulse. I know it has spark and compression cause it runs on starter fluid. So I'm a bit confused. Its got to be bad gas ill try syphoning the tank and getting new fuel in it
 
Just because the injectors spray, that doesn't mean they are spraying the correct amount of fuel.

How long can you keep the engine running on starting fluid?
 
I just removed the fuel rail and injectors it was injecting on all 4 when cranking confirming pressure and pulse. I know it has spark and compression cause it runs on starter fluid. So I'm a bit confused. Its got to be bad gas ill try syphoning the tank and getting new fuel in it
I guess I missed the edit ten minutes later that it didn't have gas in it. How were the injectors spraying with no gas.....

Glad you got it running.

I noticed tbrickers are learning the ways of using a can of starting fluid as a cheap DIY diag tool. That's great.
 
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I guess I missed the edit ten minutes later that it didn't have gas in it. How were the injectors spraying with no gas.....

Glad you got it running.

I noticed tbrickers are learning the ways of using a can of starting fluid as a cheap DIY diag tool. That's great.
There will still be some fuel in the lines when tank is near or empty

Brake kleen in any of the vacuum ports works very well.
 
Brake kleen in any of the vacuum ports works very well.
Idk if its a CA thing or the specific brand we use but I've had trouble recently using brakeclean as starting fluid. Now I spring straight for a can of the good stuff

I noticed tbrickers are learning the ways of using a can of starting fluid as a cheap DIY diag tool. That's great.
Almost like it's a half dozen birds with one stone move
 
Yeah I know. It wasnt quite clear what was going on. That's why I recommend starting fluid/brakleen/Hairnet. If the timing is off you get some fun backfires!
 
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