Hot start issue 99 Mounty 5.0

[koda2000]

I say Fuel Regulator - I wd also have changed IAC.

Please explain your thinking on the IAC. How does a bad IAC prevent starting when hot? Do you mean the ECT sensor, or perhaps the air intake/temperature charge sensor?

I think the PO has stated he recently replaced the entire fuel pump assembly and I think the 99's had the return-less fuel system (not 100% sure of that). If so are you suggesting that he's had 2 bad FPR's in a row? To that I'd say, highly improbable. If the '99 still used the return-style fuel system, I've already suggested he test the FPR at the fuel rail. Throwing money and parts at a problem w/out knowing what the actual problem is a waste of money. Fuel possibly leaking into the engine when hot (flooding it) due to leaking fuel injectors or leaking rail mounted FPR/FP modulator are fairly easy to diagnose and should be eliminated as possible issues.

 

[410Fortune]

I never found out if the pressure regulator in the tank was replaced

1999 is returnless fuel

 

[koda2000]

I never found out if the pressure regulator in the tank was replaced

1999 is returnless fuel

I was pretty sure the '99 was return-less, but never owning a '99 I wasn't sure. As the in-tank FPR on the return-less fuel system is strictly mechanical about the only thing that can go wrong with it is that the plastic housing can crack and leak fuel pressure. While that can happen it's not a common issue and can visually be verified. Besides, if the FPR is bad that doesn't explain why it would only cause problems during hot starting.

 

[410Fortune]

in fact 99.9% of the 98's I see are returnless so by 99 they all are

For me a hot start issue is USUALLY not enough fuel pressure........a weak pump
especially when they say "prime the key a few times and it will start"
Seems like the fuel pump is not able to keep up with demand when hot = faulty pump, crappy install, or bad fuel pressure regulator or?
So the BEST THING TO DO is CHECK FUEL RAIL PRESSURE when hot... a 99 should still have a schrader valve
The only other thing that causes a hot no start is the crank sensor

In post 1 the OP says he replaced fuel pump with all motorcraft parts....I just wanted to know if it was the whole in tank unit or just the pump.
Guessing this issue was there before the pump replacement.
Lots of guessing when questions go un answered....................................................

 

[dr fildo]

It finally just threw a code right now. I'll check that in a few hours and see what it points to.

 

[dr fildo]

in fact 99.9% of the 98's I see are returnless so by 99 they all are

For me a hot start issue is USUALLY not enough fuel pressure........a weak pump
The only other thing that causes a hot no start is the crank sensor

In post 1 the OP says he replaced fuel pump with all motorcraft parts....I just wanted to know if it was the whole in tank unit or just the pump.
Guessing this issue was there before the pump replacement.
Lots of guessing when questions go un answered....................................................

Yes, it was the entire fuel pump assembly in the tank.

 

[dr fildo]

Yes, it was the entire fuel pump assembly in the tank.

Yes, I had this problem before I replaced the fuel pump assembly. It absolutely runs much better, but didn't solve my problem.

 

[410Fortune]

CODE!!!!!!!!!!!!!! yes get the code. I love PCM codes.................... points right to the issue

 

[Mbrooks420]

What was the brand of sending unit you installed?

 

[410Fortune]

Just replaced ECT sensor and fuel pump. New Motorcraft parts.

 

[BUXTER]

Please explain your thinking on the IAC. How does a bad IAC prevent starting when hot? Do you mean the ECT sensor, or perhaps the air intake/temperature charge sensor?

I think the PO has stated he recently replaced the entire fuel pump assembly and I think the 99's had the return-less fuel system (not 100% sure of that). If so are you suggesting that he's had 2 bad FPR's in a row? To that I'd say, highly improbable. If the '99 still used the return-style fuel system, I've already suggested he test the FPR at the fuel rail. Throwing money and parts at a problem w/out knowing what the actual problem is a waste of money. Fuel possibly leaking into the engine when hot (flooding it) due to leaking fuel injectors or leaking rail mounted FPR/FP modulator are fairly easy to diagnose and should be eliminated as possible issues.

I concurred with u that IF APPLICABLE FPIR on Fuel Rail most likely in this instance (looks like its NA) - IAC can be involved in any start problem Hot or Cold & yes of course ECT tells PCM to tell IAC Engine is Hot or Cold - I definitely wd have checked both before Fuel Pump.

 

[410Fortune]

fuel pressure test should be the first thing done!! Anytime there is a hot start issue AND priming the pump with key results in a start

 

[dr fildo]

fuel pressure test should be the first thing done!! Anytime there is a hot start issue AND priming the pump with key results in a start

For a while, priming the pump a few times before start was working when hot. Now it doesn't.

Replacing the fuel pump assembly definitely makes the engine run MUCH better, as I assume the original pump would be tired after 243,x.. miles. Not THE problem, however.

 

[koda2000]

@dr fildo - At this point there is not much that further speculation on our part can do for you. You have to start gathering some facts. Fuel pressure at the fuel rail (cold and hot), pull OBD II trouble codes and report, follow the suggestions made to narrow your problem down.

 

[dr fildo]

@dr fildo - At this point there is not much that further speculation on our part can do for you. You have to start gathering some facts. Fuel pressure at the fuel rail (cold and hot), pull OBD II trouble codes and report, follow the suggestions made to narrow your problem down.

Agreed. I will follow up as soon as I have more info.

The help from everyone is GREATLY appreciated.

 

[dr fildo]

What was the brand of sending unit you installed?

The entire unit was Motorcraft

 

[410Fortune]

heck yeah dude! we need some info
You gotta check the fuel rail pressure when the no start issue occurs
As a mechanic all we can do is check things off a list, eliminate them as the cause
You do NOT want to "load the parts shotgun" that does not a good mechanic make

 

[dr fildo]

I drove around a bit yesterday. The problem only happened once. I held the accelerator down 1/4 of the way and it started. It has been starting without the accelerator or the "key on/key off" cycle tricks, but with long cranks, which is an improvement to the no starts at all.

The oil does not smell like gasoline.

I don't have a pressure gauge to measure it yet.

The code is P0455 which is an evap code (large leak). This is a code that it has been throwing occasionally for some time.

I also started it and took some live data (24 items of data) but I'm not sure what to do with that or if it would even help.

 

[koda2000]

The vac leak is unlikely to have any impact on your hot-start issue. The fact that you've had better luck hot-starting it awhile cracking the throttle body open 1/4 way suggests the engine is getting flooded.

After letting an engine cool down (or sit overnight) any excess fuel in the cylinders evaporates and the engine starts normally. When you get your hands on a fuel pressure gauge and measuring the fuel pressure at the fuel rail cold (and when hot) you may find the pressure looks normal (around 65-67 PSI for the return-less style fuel system). However, if you're leaking fuel the pressure at the rail may drop quickly. After leaving my Sport Trac sit for many months, I was quite surprised to find there was residual fuel pressure when I pulled the fuel line from the fuel rail. IIRC you should see your pressure gauge holding near 60-65 PSI for an hour or more. If the pressure drops off in a matter or minutes something is leaking. As you recently installed a new OEM fuel pump assembly it's not likely your FPR is your problem. That leaves possible leaking injector(s) or perhaps a bad fuel pressure modulator, which is allowing fuel to leak into the intake.

As I said earlier, testing the fuel pressure modulator's diaphragm with a cheap (around $20) hand-held vacuum tester pump is easy enough and you can borrow a fuel pressure gauge from most auto parts stores.

 

[dr fildo]

The vac leak is unlikely to have any impact on your hot-start issue. The fact that you've had better luck hot-starting it awhile cracking the throttle body open 1/4 way suggests the engine is getting flooded.

After letting an engine cool down (or sit overnight) any excess fuel in the cylinders evaporates and the engine starts normally. When you get your hands on a fuel pressure gauge and measuring the fuel pressure at the fuel rail cold (and when hot) you may find the pressure looks normal (around 65-67 PSI for the return-less style fuel system). However, if you're leaking fuel the pressure at the rail may drop quickly. After leaving my Sport Trac sit for many months, I was quite surprised to find there was residual fuel pressure when I pulled the fuel line from the fuel rail. IIRC you should see your pressure gauge holding near 60-65 PSI for an hour or more. If the pressure drops off in a matter or minutes something is leaking. As you recently installed a new OEM fuel pump assembly it's not likely your FPR is your problem. That leaves possible leaking injector(s) or perhaps a bad fuel pressure modulator, which is allowing fuel to leak into the intake.

As I said earlier, testing the fuel pressure modulator's diaphragm with a cheap (around $20) hand-held vacuum tester pump is easy enough and you can borrow a fuel pressure gauge from most auto parts stores.

Ok, I was finally able to pressure test the fuel rail. 65 lbs when running. After the engine is hot and shutting off; after 1 hour the pressure was down to 28 lbs. Started right up with no problem. Pressure goes down very slowly. And since the last post about a week ago, I only had the hot start problem once. And not while I was pressure testing.

I'm lost.