Hard start when warm only. Cold/Hot is fine.

[Camelopardalis]

EDIT: For those searching for a resolved extended cranking issue when warm, it seems to be the check valve in the fuel hanger. I was easily able to blow back through mine and I was losing fuel pressure after shutting off the engine when warm. Ordered a new hangar including pump from RockAuto and it fires up immediately under all conditions now.

Hey guys,

I've had my Explorer for about 6 months. It's a 1999 5.0 AWD with 206K km (About 130k mi). Runs very well, pretty low mileage but I expected that with the AWD V8. It gets fairly good mileage on the highway, no power loss, missing or stumbling. I tow with it as well without issue up to 2000lbs.

My issue is that under a WARM start only it excessively cranks until it fires. I don't remember this happening on either time I test drove it, but it needs to be pretty certain (easily repeatable) conditions. Once firing, it will stumble for a moment, pick up and run fine again. If i turn the key twice instead of just turning to start (I.e. prime it twice, it fires up normally). When hot (~up to 20 minutes since driving) it fires up immediately. Fires up very well dead cold as well.

Now the history. I purchased it, drove it home. Changed the water pump, coolant, fuel filter, and oil and cleaned out a bit under the hood and I had to clean around the blower motor area due to some mice issues. The nest was isolated there, I have no other electrical issues that I know of besides factory radio screen only turning on if its very cold out (which is a known issue). I also changed plugs a while later as preventative maintenance along with resealing the rear diff (and new oil as it was leaking).

I also cleaned off the crank sensor, cleaned the connector and also disconnected the 2 large connections near the windshield on the firewall and cleaned those as well. No change. Has new battery and the previous owner replaced the alternator. I have a new crank sensor, new oil pressure and new coolant temp sensor on the way for piece of mind since I had to order a ball joint and wipers anyway. Once those are in I will report back as well.

In the meantime, I've read a bunch of threads and it seems lots of people have this issue. The ones that seemed to be resolved stemmed from the crankshaft sensor but most of them just went nowhere. I'm hesitant to change the fuel pump as I have good pressure at the rail (was within spec when tested) both hot and cold, it's only warm it seems to fail to pressurize until it starts cranking. If anyone has any suggestions or has gone through this themselves please advise and if you need more info or diagnostics let me know.

Thanks,

Joel

P.S. When this gets resolved, I will edit this post or post a complete one at the end for those looking for answers on this subject through the search.

 

[Camelopardalis]

New crank sensor and coolant temp sensor changed nothing, guess I am going to hail mary the fuel pump. Seems to do it less now that its -30, not sure what it would be tied to at this point.

 

[Turdle]

Which coolant "sensor" did you change? picture please because there are 2 of them, one is for the gauge only, the other is the one which can give the problem.

 

[Camelopardalis]

Which coolant "sensor" did you change? picture please because there are 2 of them, one is for the gauge only, the other is the one which can give the problem.

Thanks for the reply Jon,

It was the ECU sensor (2 blade terminal, I attached a stock photo as well). Location was (looking at the engine from the front) top of the engine on the left side facing towards the passenger front partway under the manifold. Bit of a bear to get, but not bad. Also running a scanner on the vehicle nets an accurate coolant temp reading through the OBDII port, so it seems to be functioning fine at this point.

Joel

 

[koda2000]

My 2001 5.0L Eddie Bauer did the "sometimes no-start when warm" for years. Cold or hot it always started fine. It finally got a no-start after sitting in the cold garage for a month+ during the winter. Couldn't hear the fuel pump prime (first time it wouldn't start when it somewhere quite enough to hear it). Got it to start one last time by turning the ignition key from OFF to ON at least 50 times. Changed the fuel pump using a Bosch 69128 replacement pump kit (around $45 on eBay) along with a new fuel filter and strainer sock. That was around 3 years ago. It's been starting instantly ever since - cold, warm and hot. I had around 195K on the EB at the time. That seems to be the average life span on the original OE fuel pumps. I've had to change 5-6 other 2000 & 2001 Explorer/Mountaineer fuel pumps, all between 175K-210K. I used the Bosch 69128 pump kit for all of them.

 

[Turdle]

^^ I second this.

 

[koda2000]

^^ I second this.

Yeah, this was the only one of the 6-7 fuel pumps I've had fail that didn't begin by giving intermittent "no start" problem when the weather turned cold and then only on the first start of the day.

 

[Camelopardalis]

Alrighty guys,

So I ended up pulling the fuel pump out and replacing the pump and hanger. The one way valve inside was whacked and I was losing fuel pressure and it wasn't priming long enough when warm. Long story short, new pump/hanger and she fires up instantly. Pretty easy to change, getting the fuel line off took longer than the rest of the job I'd say.

Thanks for the help everyone, glad it's resolved.

On a side note, I picked up 2 new 02 sensors. Drivers side was cake, the passenger one is brutal. For anyone searching this thread it's on top of the passenger side just in front of the cat and it's easier to remove the center console and carpet unless you have tiny arms.

Joel Kramer

 

[koda2000]

Alrighty guys,

So I ended up pulling the fuel pump out and replacing the pump and hanger. The one way valve inside was whacked and I was losing fuel pressure and it wasn't priming long enough when warm. Long story short, new pump/hanger and she fires up instantly. Pretty easy to change, getting the fuel line off took longer than the rest of the job I'd say.

Thanks for the help everyone, glad it's resolved.

On a side note, I picked up 2 new 02 sensors. Drivers side was cake, the passenger one is brutal. For anyone searching this thread it's on top of the passenger side just in front of the cat and it's easier to remove the center console and carpet unless you have tiny arms.

Joel Kramer

Congrats!

Thanks for getting back to us with the resolution. I know what you mean about getting the fuel line loose from the pump assembly. It's a bear to get to release.