Terrible Starting

[Dave K]

2006 24V Power marine 6.0L Vortec

I have read up on a search and there seems to be a number of possibilities but here I go with my problem. I am not a mechanic by any means so any help would be appreciated.

Cold start- cranks-turns over- sputters for a few seconds and I give it alittle throttle in nuetral and then it runs like a champ.

After being on the water, when we turn off engine it is absolutely horrible and almost impossible to start when it is hot. Yesterday we spent better part of 1/2 hour-45 minutes trying to get it going. Finally it turned over and fired after giving it anywhere from 1/2 to full throttle in neutral. We did take out the fuel pump rely and cranked it for a bit so it wouldnt flood itself.?

Now here's the kicker...apparently the dealer installed the update kit which returns the hot fuel back to the tank so the pump can draw cooler fuel. This return line runs from the engine basically runs side by side with the fuel line down to the floor, forward a foot or so, then up the height of the tank and in. I'm thinking that if this return line is just gravity feed the hot fuel wouldnt make it back in to tank because of the low spot in that return line. Does that make any sense or am I grasping at straws?

I really don't care how much $'s it takes to fix because it is still under warranty. I am wondering if anyone could throw some suggestions at me so I can take a list of possibilities to the dealer.

[ajholt7]

I don't believe the return line is your problem. I routed mine the same way and it solved my vapor lock issues.

[chpthril]

ETC (Engine Coolant Temp) sensor can be the cause of both your cold and hot starting problems. This is NOT the the same temp sendor that supplies the gauge.

[Dave K]

I don't believe the return line is your problem. I routed mine the same way and it solved my vapor lock issues.

The dealer said it was gravity feed and then he said there was 4 psi.... but If yours work with the way the return line is run (low spot before tank), that more than likely rules out that update kit.

Thanks

[Dave K]

ETC (Engine Coolant Temp) sensor can be the cause of both your cold and hot starting problems. This is NOT the the same temp sendor that supplies the gauge.

Hey Mike,

Can you tell me where that ECT sensor is located?

I have a semi closed cooling system...could it be something as simply as coolant not be strong enough?

[ajholt7]

The dealer said it was gravity feed and then he said there was 4 psi.... but If yours work with the way the return line is run (low spot before tank), that more than likely rules out that update kit.

Thanks

Mine does have a low spot before the tank. I don't know what the pressure is but it is not gravity fed. It tees in to the return line from the fuel rail.

[chpthril]

Hey Mike,

Can you tell me where that ECT sensor is located?

I have a semi closed cooling system...could it be something as simply as coolant not be strong enough?

On an automotive engine, it would be located in the intake manifolds coolant ports near the thermostat housing. Probably a 2 wire sensor.

[Dave K]

My boat is sitting at the lake and Marine Power has not responded to me yet. I was wondering if anyone would know if GM 15326388 is the part number for ECT sensor?

Also is there a web site that details part numbers?

[boatwakes]

Dave, first, I'm leaning toward Idle Air Control valve problem. Second, your return line will always be under pressure as it is being fed by the low and high pressure pumps in the system returning unused fuel. Third, when trying to start with throttle applied, the MEFI computer systems will STOP supplying fuel through the injectors when throttle position reaches 50% or more so only give it a slight increase when trying to start the engine. If it starts when slight throttle is applied but not when no throttle is applied, pull the IAC, clean and reinstall or replace...or get a code scanner and plug in to see for sure.

[Dave K]

Dave, first, I'm leaning toward Idle Air Control valve problem. Second, your return line will always be under pressure as it is being fed by the low and high pressure pumps in the system returning unused fuel. Third, when trying to start with throttle applied, the MEFI computer systems will STOP supplying fuel through the injectors when throttle position reaches 50% or more so only give it a slight increase when trying to start the engine. If it starts when slight throttle is applied but not when no throttle is applied, pull the IAC, clean and reinstall or replace...or get a code scanner and plug in to see for sure.

I'm not too familiar with engines but I am a hands on guy. Would you be able to tell me what that idle air control valve looks like and where to find it?

Also what is used to clean the IAC valve?

Thanks