Hard start when hot 2003 mpi 6.2 bravo

[Great lakes pirate]

I have been having a hard start condition for a while on my port engine. It starts up just fine when the engine is cold. Once I take a ride and stop for a hour or two it dosen't want to start back up. When the engine runs, it runs very well. I did check compression and a couple of cylinders are pretty low but it still runs great.

 

[jason78]

Could it be an IAC starting to go bad? Does it help to put the throttle in Neutral and give it a little gas when starting?

 

[Great lakes pirate]

Could it be an IAC starting to go bad? Does it help to put the throttle in Neutral and give it a little gas when starting?

No, I have swapped IAC's and also put a new one in and no improvement.

I have read that a cool fuel module can go bad an allow the fuel to vapor lock. Has anyone else heard of this before?

 

[ppkaprince98]

May not be the same but I had a Jeep that when the fuel line got hot it would not restart until the gas cooled down. I ended up rerouting the fuel lines and to keep them away from the exhaust and the problem went away. So I would say that its a possibility your fuel is vapor locking if its getting hot. Is there a way to check the temp of the fuel coming in, feel the line or something?

 

[skolbe]

What is the compression on it? Just curious. You said it is low. Sounds like a classic IAC issue, obviously it is not that.

 

[Great lakes pirate]

What is the compression on it? Just curious. You said it is low. Sounds like a classic IAC issue, obviously it is not that.

The highest was 175 and the lowest was 115. I may be due for a valve job (700 hrs). It still runs VERY well and strong. It is only a problem during a hot start.

 

[Great lakes pirate]

I replaced the fuel cooler over the weekend. I still have the hard start when hot condition. It fires right up when it is cool but as soon as it gets up to temp it will not start. I am thinking that one of the sensors is sending out some funny outputs and the computer is adjusting the timing to the point where it will not start.

 

[Alex F]

This definitely doesn't sound like IAC issue if it fires up and idles fine when cold. Do you have SC (I forgot what was the first year they came on 320s)? If yes, any codes?

 

[Great lakes pirate]

This definitely doesn't sound like IAC issue if it fires up and idles fine when cold. Do you have SC (I forgot what was the first year they came on 320s)? If yes, any codes?

No smart craft on this boat. I do have a rinda scan tool. I plugged it in at the end of last year and there were no faults. I was having this problem last year also. I think my next move will be to warm up the engine, turn it off, plug in the scan tool and try to re-start.

 

[KHE]

Just a thought but does your engine have a supply and return fuel line with a fuel pressure regulator on the fuel rail? If so, unplug the vacuum line to the fuel pressure regulator and check the nipple for gasoline. If there is fuel smell in the vacuum line or the nipple on the fuel pressure regulator itself, the fuel pressure regulator is bad. A bad fuel pressure regulator will dump unmetered fuel into the mixture. The extra fuel will not cause a problem on cold starts as the extra fuel acts like a choke on a carbureted engine. It will cause a hard starting issue on a warm engine though.

Another way to test is to unplug the vacuum line while the engine is idling and if any fuel comes out of the nipple on the fuel pressure regulator, the problem is the fuel pressure regulator.

 

[Great lakes pirate]

Just a thought but does your engine have a supply and return fuel line with a fuel pressure regulator on the fuel rail? If so, unplug the vacuum line to the fuel pressure regulator and check the nipple for gasoline. If there is fuel smell in the vacuum line or the nipple on the fuel pressure regulator itself, the fuel pressure regulator is bad. A bad fuel pressure regulator will dump unmetered fuel into the mixture. The extra fuel will not cause a problem on cold starts as the extra fuel acts like a choke on a carbureted engine. It will cause a hard starting issue on a warm engine though.

Another way to test is to unplug the vacuum line while the engine is idling and if any fuel comes out of the nipple on the fuel pressure regulator, the problem is the fuel pressure regulator.

Yes, I am pretty sure there is a fpr on the fuel rail. I will check that out next time I get to the boat. My engines are MPI. Does this problem occur on fuel injected engines also?

 

[KHE]

Yes, I am pretty sure there is a fpr on the fuel rail. I will check that out next time I get to the boat. My engines are MPI. Does this problem occur on fuel injected engines also?

Yes - I was speaking about a fuel injected engine - MPI. The comparison I made to the carb'd engine was to explain why the engine would start OK when cold but not warm.

You can remove the vacuum line from the FPR and turn the key to ON without starting the engine and check to see if any fuel comes out of the FPR nipple. If you smell fuel at the nipple, start the engine and then remove the vacuum line and observe the nipple. If fuel drips out, then you know the FPR is bad.

Good luck and post back your findings.

 

[Alex F]

.... I think my next move will be to warm up the engine, turn it off, plug in the scan tool and try to re-start.

I think that's a good idea. You want the reading to be done when the issue occurs.

 

[Great lakes pirate]

Back to the boat tonight after work. I checked the fuel pressure regulator like KHE suggested and there was no smell/signs of gas. I then plugged in my scan tools and checked to see if there were any active fault codes. There were no codes so I fired it up. I checked to see if any gas would come out if I unhooked the hose on the FPR and it was functioning properly. I let it warm up for about 5 minutes and wrote down all of the PCM data (Water temp, throttle position sensor, IAC percentage, spark advance, manifold temp and pressure) to compare with the good engine. The numbers were pretty much the same across both engines.

I then let the bad engine sit for 10 minutes and it fired right back up with no faults. I shut it down and started it back up a couple more times over a 30 minute period and finally said screw it. I put everthing away and closed the hatch. I tried to start it one last time and crank, crank, crank, crank, crank..... Bas****.

Open the hatch, plug in the scan tool and no faults. I tried to start it 4 more times.... NADA.

:smt119

 

[scoflaw]

Check your fuel pressure. Shrader valve on the fuel rail. Should be around 43.

 

[Great lakes pirate]

Check your fuel pressure. Shrader valve on the fuel rail. Should be around 43.

Fuel pressure is around 43 when the pump turns on then fades to about 35 and stays there. I am starting to think the pressure is good but the flow rate is low. Not sure why it runs fine, starts fine when cold but when its hot doesn't want to start....

 

[scoflaw]

Shouldn't drop to 35. Cool fuel 3's have been having the paint issues plugging things up

You have already checked the filters, right?

Whats the fuel pressure doing on the other engine?

 

[Great lakes pirate]

Shouldn't drop to 35. Cool fuel 3's have been having the paint issues plugging things up

You have already checked the filters, right?

Whats the fuel pressure doing on the other engine?

My boat has the cool fuel 2 set up. The other engine has about the same fuel pressure. I replaced the water seperating filter as well as the in-line filter. Are there any other fuel filters? I was talking to a mechanic and he suggested that I take a look at the low pressure pump to see if there was any gunk blocking the intake side screen.

 

[Alex F]

... I was talking to a mechanic and he suggested that I take a look at the low pressure pump to see if there was any gunk blocking the intake side screen.

IMO, if there's a physical blockage, then it shouldn't matter if the engine is hot or cold. The affect should be the same.

 

[scoflaw]

Does your fuel pressure hold steady for a good long time after the motor is shut down? Leaky injectors will cause hard hot starts

Is that motor running hotter than the other, like in heat soak? Try running your blower to see if it helps symptom.