No start when warm

[David Foster]

New member here. Bought a 02 ranger 4.0 SOHC 5spd ext cab 4wd while working out of town with known engine issues. Pickup came with a second 2003 donor pickup with good engine but automatic. Ended up doing heads, timing chains, oil pump, water pump, injectors, and all new seals on engine before swapping. Pickup starts and runs great until you shut it off and try to restart. Usually has to sit upwards of an hour then it will start. Replaced fuel pump, crank position sensor, cam position sensor, both temp sensor and switch, ecm and still same results. Give it a shot of either and it fires right up. Check engine light comes on with key but only sometimes flashes when cranking. Injectors have power but testing the ground pulse it seems intermittent. Electrical issues tend to get the better of me since I make a living shorting things out on purpose( I'm a welder). MAF sensor, IAC all seem to check out. I'm at a loss and would appreciate any insight. Thank you in advance. Pictures are my sons 98 we rebuilt tranny on then he promptly hit a deer. Made it a little less deer friendly

 

[Curious Hound]

Almost (but not quite) sounds like a loose connection on a circuit board for something. Heats up, opens connection, won't start again u til cool. But ai would expect that kind of problem to make it quit or run rough when warm. My other gut feeling is vapor lock in the fuel system.

 

[Uncle Gump]

I moved your post to the 4.0L forum...

Put a fuel pressure gauge on it when it won't start. Firing with starting fluid makes me believe fuel system.

Have you looked at the fuel pump relay and connections real well?

 

[David Foster]

I moved your post to the 4.0L forum...

Put a fuel pressure gauge on it when it won't start. Firing with starting fluid makes me believe fuel system.

Have you looked at the fuel pump relay and connections real well?

Fuel pressure is 60-65lbs

 

[Mechrick]

Any codes?

I think you've established it's missing fuel. When it's acting up, will it bump start (assuming it's still a 5 speed)? Sometimes the current draw through the starter and the accompanying magnetic fields can mess with the crank/cam sensors. Old GM cars had make-specific distributor pickups that were wound to match the starter and mismatches would have the same symptom.

 

[David Foster]

Fuel pressure is 60-65lbs

It sure seems like I'm not getting a consistent injector pulse until it's running

 

[David Foster]

Any codes?

I think you've established it's missing fuel. When it's acting up, will it bump start (assuming it's still a 5 speed)? Sometimes the current draw through the starter and the accompanying magnetic fields can mess with the crank/cam sensors. Old GM cars had make-specific distributor pickups that were wound to match the starter and mismatches would have the same symptom.

I haven't tried that. I'm usually on the flats and by myself when messing with it. When I get a chance I'll either shut it off on a hill or find some help and drag it. Thanks

 

[David Foster]

Almost (but not quite) sounds like a loose connection on a circuit board for something. Heats up, opens connection, won't start again u til cool. But ai would expect that kind of problem to make it quit or run rough when warm. My other gut feeling is vapor lock in the fuel system.

Circuit board in the ECM? Or fuse relay panel? The only issue is cranking. No blubbering stuttering at all once running

 

[Uncle Gump]

Fuel pressure is 60-65lbs

Even when it won't start?

 

[Curious Hound]

Circuit board in the ECM? Or fuse relay panel? The only issue is cranking. No blubbering stuttering at all once running

Now I'm confused about your symptoms. Cranking = starter motor is rotating the crank and trying to start the engine. You said earlier that it will start on ether. But now you say it has trouble cranking. Which is it? It has to crank to start on ether.

 

[David Foster]

Now I'm confused about your symptoms. Cranking = starter motor is rotating the crank and trying to start the engine. You said earlier that it will start on ether. But now you say it has trouble cranking. Which is it? It has to crank to start on ether.

While cranking. Starter is fine.

 

[David Foster]

Even when it won't start?

Yes. It's had a fuel pressure gauge on it since i first noticed the issue

 

[Curious Hound]

If you really think your injectors aren't firing right, that would point to the ecu. I would check grounds and other connections to the ecu. But, if it only happens during starting, that may also point to cam position signal and crank position signal.

The part I said about loose connection on a circuit board may be a possibility. A loose or cracked solder joint on the ecu. And, Ranger ecus are known to have a problem with capacitors going bad as they age. This gives some really weird symptoms sometimes. There are 2 or 3 (usually blue) capacitors in the ecu. They arent real difficult to replace if you are handy with a soldering iron. Open it up, read the writing on the sides of them and match the specs with an electronics parts seller online. You're mostly concerned with the capacitance value - probably has units of "mfd" ( microfahrads) and voltage rating. You want "electrolytic capacitors". Not ceramic ones.

 

[David Foster]

If you really think your injectors aren't firing right, that would point to the ecu. I would check grounds and other connections to the ecu. But, if it only happens during starting, that may also point to cam position signal and crank position signal.

The part I said about loose connection on a circuit board may be a possibility. A loose or cracked solder joint on the ecu. And, Ranger cups are known to have a problem with capacitors going bad as they age. This gives some really weird symptoms sometimes. There are 2 or 3 (usually blue) capacitors in the ecu. They arent real difficult to replace if you are handy with a soldering iron. Open it up, read the writing on the sides of them and match the specs with an electronics parts seller online. You're mostly concerned with the capacitance value - probably has units of "mfd" ( microfahrads) and voltage rating. You want "electrolytic capacitors". Not ceramic ones.

I also assumed an ECU issue so I replaced it with a reman. When they opened up the old one (after I installed the new one) they said they couldn't find anything wrong

 

[Mechrick]

Perhaps check the VPWR voltage at the injectors while cranking. Reference the ground with the same ground as the PCM. There's usually a ground wire that attaches to the engine block or fuel rail for the injectors' ground path. The PCM will start to drop function at about 9 volts.

In general, since this problem started after installing the engine, verify that the PCM ground at the negative battery terminal, the sheet metal ground to the inner fender (or core support) and the main starter ground from the neg battery terminal to the engine block close to the starter are all intact.