[SOLVED] 4.0 SOHC is long cranking when hot

[koda2000]

I'm running out of ideas for you. What is your MPG? Does it seem normal? I'm not am expert on the 4.0L OHV, but the 2 other engines normally get around 15 'ish city and 20 'ish hwy.

If it's not getting too much fuel when warm, is it possible it's not getting enough? That doesn't make sense though as cranking it with the gas pedal to the floor when warm is getting it started. Have you tried cycling you key ON/OFF a few times when warm to prime the fuel system?

One problems the OHV engines suffer from is cracked heads. These tend to be very small cracks that occur between the valve seats. These hair-line cracks can be so small that they can even close up one the engine heats up. Perhaps as the engine cools the cracks open up and leak coolant into the combustion chambers? This might cause hard starting, but the cooler the engine gets the worse it would be. Have you recently overheated? Do you find you are mysteriously loosing coolant (even a small amount)?

What kind/brand of spark plugs do you have in the engine? Fords don't like Bosch spark plugs for some reason and most here use Motorcraft or Autolite double platinum plugs, which seem to work the best in these engines.

The cam position sensor is responsible for fuel timing. I've read that the engine should run even with a bad cam sensor, though badly, but I've also recently read that sometimes the will not run at all.

Finally, have you said you've replaced the pre-cat O2 sensors. They effect fuel trims.

I never like throwing parts at a problem w/out a reasonable assurance they will solve the problem (especially expensive parts). I know what starter motor heat-soak is. It effects the speed at which the starter spins. Nothing else. If you find that the starter seems to be spinning at the same speed cold and hot then that's not your issue. If your starter has started making weird noises, it's probably a worn bushing, but as long as the motor still spins normally that's not an urgent issue.

 

[slisman]

Hey, sorry for little brake in this topic but I've been dealing with IFS bushings - all front suspension has new bushings and joints

And now back to hard start problems.

1) MPG is pretty normal, I've new, good O2 sensors. It's about 16 mpg. And all fuel trims are in perfect thresholds

2) Cycling key ON/OFF does not help. So in my opinion fuel pressure regulator is not suspected, the same as fuel pump and fuel lines.

3) I have never overheated engine, it hold temperature perfectly (I have external gauge). Previous (very small) looses of coolant probably were caused by leaks in cooler and leaks near the thermostat (fixed with no further observations). Is head cracked? Hope not, but I've been thinking about it.

4) I have OEM motorcraft cables and Autolite plugs - I know issues with bosch spark plugs Both have about 1.5 years and 10 000 miles.

5) Starter thing seems not logical all in all.

And from my new observations/issues:
6) Can Evaporative Emission Canister Purge cause such issue? There are not trouble code, but live view at PID in forscan "Evaporative Emission Canister Purge Fault" show "YES FAULT". I am totally not familiar with this system, but I've found something like that "When the engine is running and fully warmed up, the engine computer gradually opens the purge valve to allow some amount of fuel vapors to be moved from the charcoal canister and burned in the engine." Maybe it is the issue? Is way to check it, i.e. by temporarily closing this valve or bypassing it? Maybe engine is flushed by fuel vapors?

7) I am trying to check voltages of each sensor in forscan/manually, but I have no more ideas what to check.

Thanks for help and every idea again!

 

[koda2000]

I do not believe that any fault in the evap system could have an effect on hot/warm starting. The purpose of the evap system is to store gasoline vapor in the charcoal canister until the engine is started. Then the purge valve is supposed to open to allow the gas fumes to be sucked into the engine and burned.

About the only engine running thing I can imagine an evap system fault could have is if it has a vacuum leak, which would cause a lean condition. Nothing to do with hot/warm starting.

 

[slisman]

Right. So broken/open valve should not cause such problems?

- I will try to check MAF sensor - voltages and o2/s ratio.

- EGR valve could be stuck open and be responsible for this issue? It's easy to try and "close it".

- Small smell of gas in intake - maybe it can be a trace?

- And maybe problems with engine computer?

Lack of further ideas

 

[koda2000]

Right. So broken/open valve should not cause such problems?

- I will try to check MAF sensor - voltages and o2/s ratio.

- EGR valve could be stuck open and be responsible for this issue? It's easy to try and "close it".

- Small smell of gas in intake - maybe it can be a trace?

- And maybe problems with engine computer?

Lack of further ideas

Above are good things to check. Did we discuss the possibility of a leaky fuel injector? Seems we did, but I can't recall.

 

[410Fortune]

You need to check your fuel rail pressure, I know you have replaced the pump twice and the filter, but you never tested the rail pressure.
A bad regulator can allow too much pressure or too little

 

[koda2000]

@slisman - Did you replace just the fuel pump or the whole FP assembly. Sounds like you replaced just the pump. In the return-less fuel system the regulator is the black thing just above the fuel pump. It's pretty rare that this type of regulator goes bad, unless it's housing cracks (which can happen).
On a 2000 your fuel pressure should be around 65 PSI. I think you said you checked it and had about 60 PSI, which seems pretty close to what it should be. These trucks have been known to run (not well) with as little as 20 PSI.

At a time when you know it is going to give you a "long crank/no start" by all means check the fuel pressure at the rail and see if it appears normal. This is certainly a lot easier than dropping the damn tank again and spending the money for a complete FP assembly w/out knowing it that's your problem. As far as I know, the in-tank FP regulator is not available separately.

 

[slisman]

@koda2000
-I've checked leaky fuel injectors as you adviced (thanks for this method - easy&quick!) - they seem to be good. I've unplug fuel pump relay to shut off engine. Wait 1 hour and than start - issue was present so that we can assume that injector is not leaking. Is there any chance that this method won't be good to check if injector is leaky?
-MAF voltages and work is correct I think (just checked)

@410Fortune and @koda2000 - as we talk about fuel pressure and FPR - I've just finished testing it. Seems good to me:
-Pressure after turning key on is 2.5 bar (36 psi)
-Pressure after idle is 4.5 bar (65 psi)
-Pressure held after 30 minutes is 2.5 bar (36 psi)
-Pressure after turning key on after above 30 minutes goes directly to 4 bar (58 psi)
-Pressure after FIRST try of idle (1,5 sec of cranking without idle) is 4.5 bar (65 psi)

Above pressures are good due to haynes manual. Pressure hold check after 5 minuters should be minimum 30 psi. Operating fuel pressure should be 65 psi.
I've replaced FPR year ago (OEM from another car with small mileage), I've replaced also all lines intank with special care to FPR housing - I'am familiar with this issue

To sum up:
-I will try with cut off EGR (can it help?)
-I will try to gain info about this EVAP system, maybe it is still stuck open and vapor gas are distilling into engine and it is flooded like with leaky injectors?

 

[koda2000]

I see no way the evap system can be flooding the engine, but at this point I'm out of ideas. Have you examined the DPFE and it hoses for holes/leaks? I don't see why this would cause hard hot/warm starting, but the DPFE is something that has been known to get so hot it melts a hole in DPFE housing and is related to the EGR system. Just something else to look at.

 

[danno2944]

Only thing that hasn't been mentioned is bad engine ground connections, check clean and/or upgrade/add a few.

 

[410Fortune]

Way to go! Comprehensive fuel pressure test complete!
Now do not be afraid to test the rail pressure when it has the hot. long crank condition just to confirm the pump is not getting tired.
We have to keep ruling things out to get to the real issue.

 

[slisman]

1) @koda2000 today I will look at DPFE sensor. And today I will "blind" EGR (with small steel plate) to check if it helps.
2) @danno2944 Ground connections - I've checked main ground wire from battery to body and two ground wires between body and frame. Do you know any other spots? But I think that ground is good - I've checked voltage of PCM and GEM modules - when enigne off and key off they both are 11,1 V and when engine is running they both are 14,2 V.
3) @410Fortune sure, fuel pump is pretty new. And when cranking engine I am pushing pedal to metal - then injectors are cut off and engine starts smoothly. So I can agree with @koda2000 that it looks like engine is flooded. But short injectors test by koda2000 (as above) show that injectors theoretically are not leaky. Do you have any other ideas to test it?
Thanks to you it is great fun to diagnose Of course I hope case will be closed soon.

 

[Turdle]

Just throwing my thoughts in.

2nd gen issues? Try this first!

 

[koda2000]

@slisman - To clarify, you said that with accelerator pedal held to floor the engine starts smoothly... Does it start while the pedal is held to the floor, or once you lift your foot while cranking?

It shouldn't start while your accelerator pedal is being held to the floor.

Our first SOHC V6 (I know yours is an OHV) had a weird quirk that I never figured out. During the first cold-start of the day, if you tried to start the engine it would crank and start, but would run like absolute crap and/or stall, but if before attempting starting you pressed the accelerator pedal to the floor and released it before turning the key it would start smoothly. I never figured out why it would do this. Some here thought it was because the intake manifold gaskets needed to be replaced, and perhaps they did (I later learned that this is common issue with the Job 1 SOHC engine) but that didn't explain what was happening. We just got in the habit of flooring it once before trying to start the engine and (other than the horrible timing chain rattling) it would start smoothly every time. I always wondered if flooring it some how sent a signal to the PCM, even though the key was OFF, and changing something.

Just for goofs, try pressing the accelerator pedal to the floor once and release it before trying to start the engine when hot/warm.

 

[slisman]

@Turdle thanks! Great idea, I will try it today!

@koda2000 I was full of hope...but your "workaround" doesn't help In my case - I push pedal when I turn ignition on and I keep it pushed when I am cranking engine. It has not to be "to metal". And then engine idles properly with higher revs than normally (without long cranking).

 

[Tech By Trade]

Its your EGR valve, Probably not completely stuck but its got carbon in it. Leave it long enough and you will start getting codes.

 

[slisman]

@Tech By Trade I've clogged EGR with steel plate (to test it for 100%)...and it helped (I thought) - first start when warmed after 1 hour was smooth. I was happy as f*ck
But then next day - it is still long cranking when warmed. But also cold idle is smooth and instant (better than before). So it helped but my main problem is still present. Or maybe PCM reset is required after that?


And @Turdle - my main harness looks different, I will check it tomorrow (it has cover cover on rivets).

And when trying luck with forscan - I have two more potential problems:
1) EVAPCV / EVAPVM shows always 0% and evapcv show "yes fault (with no trouble code). I've read that it can cause problems with idling on hot. Have you any idea how to diagnose it without blindly changing all sensor? Maybe can I clogg it on test purposes like EGR?

2) IAT sensor show higher temp than air temp. I know that it can be caused by engine's warm but I am not sure. Voltage on 600 revs/min (neutral) is 3.11 V.

3) MAF sensor....theoretically I've checked voltages with this method How to: - MAF Sensor Test Procedure and checked with MAF unplugged - no change.
But maybe should I clean it with MAF spray or replace with another one for try (before buying)?

Would be grateful for all further ideas to diagnose

 

[Tech By Trade]

Cant plate the EGR. It controls the DPFE sensor as well. You need a functional EGR valve in order for the system to work.

 

[slisman]

Good to know. But is it not prove that EGR sensor did not cause long cranking when hot?

I have one more idea - maybe fuel injection damper (on the firewall) is leaking? I can smell gas in intake

 

[slisman]

1) On monday I will replace MAF (used and 100% working for free). I have no hope that it will help but it is worth trying.

2) Can my problem be caused by aftermarket low quality gas cap? I have such one

3) I've attached Haynes manual Photo - maybe should I check evap system?

4) Back to EGR working. Is way to diagnose it before replacing?