my bet is fuel pump. One a bad fuel pump gets hot after use it does not want to start again. Once it cools down generally you can get it going again.

 

Thanks this makes a lot of sense, and certainly a lot more than my local mechanic!

 

How would a fuel pump in the tank, not under the hood, get hot on a short trip but not a longer one?

 

OK, the Disco I doesn't have a crank censor, so it can't be that ...

 

mole1066,

If you add your vehicle type to your signature it helps. On the earlier Discos with a distributor (not CKP) there is an ignition amplifier that is also heat sensitive. Again, test for spark when this happens. The fuel pump operation can be tested with a pressure gauge on the schraeder valve on the right side of the fuel injection rail. When key turned to position 2, the pump should run for a couple of seconds, PSI should be 32 or a little better.

 

its not short trip Vs long tip. The connections are bad and as it's used it heats up from resistance. We see this often.
Also check the connector going into the top of the fuel pump. We see a lot of corrosion in this area and this will give you the same problems.

 

The Disco I does indeed have a crank sensor, 1996 thru 1999 GEMS trucks. The 1994 and 1995 with Lucas control and a dizzy do not, the dizzy IS the crank position sensor!

The biggest problem with diagnosing this truck is that the OP has failed to clearly describe the issue. If the engine "turns over" we assume it cranks normally, there is much confusion in his description of the issue. His description of "turns over" sounds like it cranks normally but either barely will start, or starts and will barely run. This isn't helping anyone help the OP. It could be as simple as a bad battery or connection or bad starter. IF it cranks over normally (I'm still not sure) it could be crank sensor, fuel pump, fuel temp sensor, failing IAC, etc, yada yada blah blah blah.

We really need an ACCURATE account of what is going on.

 

OP, Engine starts, turns over and runs with no problem. Stop some where and at times will act like it wants to turn over but never does. So it cranks up like your going to flood it. Try a couple times and several minutes to an hour later then it starts up fine. So I've read Crank Sensor,Fuel Pump,Starter etc. Is there a way to narrow it down? Today the wife tried to take it to work and she couldnt get it started. i got home an hour later and it started with no problem. Did this several times and its good. Tried several hours later I started it and again it was ok. So its not all the time. Not sure what to do?

 

Unless you want to throw parts at it, which is costly, you need to carry a few parts with you and drive around and get it to make the problem. When it is not working, unplug a plug wire, attach a spare spark plug, lay on mainifold, crank, and check for spark. No spark almost always = bad CKP (98 has one). You can pour cold water on the sensor to speed up the return to normal. Also have a small pressure gauge, you can rent/borrow one or in a pinch use one made for tires. If spark OK, attach pressure gauge to fuel rail test valve (passenger side). If pump is running, you should hear pump for a few seconds at key in positon 2. PSI should be 32 - 34. Certainly if no pump noise or no pressure have a look at electrical connections for pump under carpet in cargo area of truck.

 

While I do not condone replacing parts without proof, in this case I would go ahead and get a new crank sensor.



The crank sensor can be purchased from AutoZone in their Duralast box for about $60 and it's a genuine Lucas part. This is cheaper than towing you truck home, and if it doesn't cure the issue it isn't wasted money since you really can't diagnose the truck unless you know this sensor is 100%.