Ok my brother has 87' Jeep comanche with 4.0 liter with 200.000 plus miles on it. In the winter time its starts ok but in the summer it will start when its cold but once it warms up you are stranded it will crank all day but it will not start. I thought fuel injection was supposed to due away with vapor lock so I don't think thats what it is. He says that adding wooden clothes pins on the fuel rail (multi port injection) seem to help the starting problem, but this was near the fall when the weather got cooler. I drove the truck allot this winter and never got stranded. It does seem to crank allot more to start then most fuel injected vehicles then I am use to, I don't know if this will help diagnose the problem.
He bought the truck a year ago in the winter so problem didn't show up till this past summer, and like I said no issues with it this winter.

Thanks in advance for everone's help
Dave

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86 Miser 170,000+
2 1/4" exhaust
Holley 1920 #55
HEI MSD BLaster 2
17.8 mpg

Sounds like the fuel system isn't holding pressure after shutoff. Could be the fuel pump check valve. An EFI pressure gauge would be best to troubleshoot this.

I'd noticed the early EFI Jeeps took a fair amount of cranking even when new. I think it takes longer for the computer to recognize the cam and crank position and start injecting fuel than with other systems. '87 still has the Rennix (Renault/Bendix) EFI system so there's nothing you can do about the computer.

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Joshua

I have seen EFI setups get vapor lock, but this is usually a case of someone trying to make a backyard returnless fuel system or using a mechanical fuel pump. Not something that usually happens with a factory system. I agree with Joshie - check the fuel pressure. The only other possible cause I can think of is the coolant temperature sensor giving a false cold reading and flooding it.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

Did you find what the problem was ?

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Fast is fine but accuracy is final. You have to learn to take your time ... in a hurry
- Wyatt Earp

The renix jeeps tends to need a bit of cranking, as the computer needs the engine to get up to 300 rpm, before it starts.

If you take a look in the front corner of the engine compartment, on the inner fender, you have a ballast resistor.
This resistor is for the fuel pump.
You could try to jump this with a wire to the battery (will run the fuel pump) to find out if it bleeds down the pressure in your system, and if it makes a difference.

hmmm... have you adjusted the tps? I don't know if it would make a difference in starting, but it makes a lot of difference to the way it runs, so might be worth to try anyway.
After the tps is adjusted, you might get wierd starts, and maybe a very high idle, but just get it started (iirc) 3-4 times, and the computer will "get" that you have made an adjustment and start working fine again

Yes we did fix the problem. The temp sensor for the computer was replaced and it fixed it.

Dave

_________________
86 Miser 170,000+
2 1/4" exhaust
Holley 1920 #55
HEI MSD BLaster 2
17.8 mpg