Hard starting 5.7 when warm

[ardeprint]

I've posted regarding this issue before. This engine has had related issues for a while with this current condition as part of other symptoms. In other words, I've had different hard starting issues which I have been able to resolve only to have another develop. The latest and current is as follows.

Basically after new fuel pump, new regulators, cleaned injectors, new starter, new batteries, inspected and cleaned and tightened battery cables, new rotor and cap, spark plugs, and several computer scans, this engine has the following issue. Will start cold as it should. After running for a bit idle or regular running it will take about 8-15 seconds to start. In addition, it will only start with the throtle wide open. Next day after everything cools it starts normal.

I have read about vapor lock, but my other engine does not do this. In addition this just started last year. Before then, hard starts was never an issue.

Lately its will rough idle or stall after coming down to idle after a cruise. When this manifests itself temp is good and oil pressure is good. IAC is about 50 hour old...

I have some thoughts, but I don't want to motivate answers. What do you think?

Any ideas as to where I should look next. Mechanics just keep suggesting to change this and that, and I usually agree with what they suggest. I just have run out of parts.

Any thoughts?

[CliffA]

Lately its will rough idle or stall after coming down to idle after a cruise. When this manifests itself temp is good and oil pressure is good. IAC is about 50 hour old

just went (well, still going) through the same thing....based on these symptoms it is very likely you have an ignition related problem....the problem only manifest after the engine runs at fairly high RPM's for a while....what is happening is the water pump is moving a high volume of cooling water through the engine while running at higher RPM's so the engine temp is adequately controlled...then when you slow down after a hard run the cooling water circulation rate drops dramatically....the engine internals and block will continue to build heat because the circulation rate of the cooling water is not sufficient to quickly bring the engine temps down.....the engine block builds heat after a hard run and this high heat is transferred to anything mounted on or around the engine including electrical components....if an electrical component has become sensative to heat it can completely fail or fail partially causing all kinds of problems....then after a while and things cool down everything returns to normal...this cycle will continue each time the engine heat builds to a point that causes some degree of failure in the suspect electrical component....in the case of my engine there are 3 ignition components that can become faulty when exposed to high heat...these are the ignition coil, the ignition sensor in the distributor, and the ignition control module.....i have replaced the coil and sensor because these are relatively inexpensive....but i have not had a chance to test the boat since....if the problem still exist i will likely have to replace the control module but that is expensive at around $500....

a marine mechanic told me the best way to check to see if the control module is the culprit is to have a timing light connected to the engine while the engine is stumbling and having problems...check the timing and if it is jumping all over the place the control module is likely defective....the primary purpose of the control module is to maintain the ignition timing throughout various running conditions....

good luck...

cliff

[ardeprint]

At CliffA. Thanks for your replies past and present.

I will swap some or all of the components you mention from between engines to see if there is any difference. I think you are on to a solution...

[CliffA]

At CliffA. Thanks for your replies past and present.

I will swap some or all of the components you mention from between engines to see if there is any difference. I think you are on to a solution...

good luck...having the ability to swap parts between twin engines is a great advantage when troubleshooting problems.....

cliff

[ardeprint]

Well I swapped the ignition coils and cabkes between engines and the problem persist. So its not the coils.

[ZZ13]

Might consider swapping IACs between motors to see if that is the cause of the rough idle. The maintenance record on my boat shows IAC replacement due to failure at less than a 50 hour interval at one time. It would at least rule out another part.

Your not alone with this type of problem. I have a similar problem with my starboard engine. Seems to take a certain temp to cause my hard start (like you, takes up to 30 seconds to finally start). Seems I can get it to start right up once the temp display on the smartcraft reads around 140 for an engine temp. I am not using the trial by error method to resolve it, trying to think through it and taking readings of stuff as I think of them as its really only a slight irritation for me based on my boating habits (I don't do much starting and stopping of the engines - more of a destination boater). The only real difference in my two engines is the starboard runs the cooling water through the hot water heater. I plan to stub those off at the engine anyway for other reasons - I will be curious to see if that changes anything in the cooling of the engine.

[ardeprint]

The only real difference in my two engines is the starboard runs the cooling water through the hot water heater. I plan to stub those off at the engine anyway for other reasons - I will be curious to see if that changes anything in the cooling of the engine.

Hi Bill, I eliminated the Water Heater setup years last year. I run the heater electrically since then with no issues. My, "non issue engine," port engine ran the heater so I would not lean on that being the problem.

Regarding our Starting problem, I have read that some folks have noticed that water draining from the exhaust manifolds empties right at the fuel cooler. I personally don't think this is our problem since so does my port engine and it does not do the same thing.

Regarding, the IAC comment I have not considered the IAC valve since I replaced it about 70 hours ago. The sympstoms definitely relate to an IAC problem so I will swap it. Thanks for the input.

[Great lakes pirate]

I've posted regarding this issue before. This engine has had related issues for a while with this current condition as part of other symptoms. In other words, I've had different hard starting issues which I have been able to resolve only to have another develop. The latest and current is as follows.

Basically after new fuel pump, new regulators, cleaned injectors, new starter, new batteries, inspected and cleaned and tightened battery cables, new rotor and cap, spark plugs, and several computer scans, this engine has the following issue. Will start cold as it should. After running for a bit idle or regular running it will take about 8-15 seconds to start. In addition, it will only start with the throtle wide open. Next day after everything cools it starts normal.

I have read about vapor lock, but my other engine does not do this. In addition this just started last year. Before then, hard starts was never an issue.

Lately its will rough idle or stall after coming down to idle after a cruise. When this manifests itself temp is good and oil pressure is good. IAC is about 50 hour old...

I have some thoughts, but I don't want to motivate answers. What do you think?

Any ideas as to where I should look next. Mechanics just keep suggesting to change this and that, and I usually agree with what they suggest. I just have run out of parts.

Any thoughts?

Have you checked compression on this engine?

[ardeprint]

Have you checked compression on this engine?

No I have not. The reasons are simple
1- My symptoms do not reflect a low compression situation. Engine starts cold fine and is hard to start hot. From what I know, usually low compression manifests with a cold engine and starts better with hot.
2- Engine runs strong otherwise
3- Computer scans show good running engine. A weak engine would manifest some signs on scan
4- No smoke at anypoint, no signs of oil burning
5- Fear that there is something wrong with compression

[CliffA]

Well I swapped the ignition coils and cabkes between engines and the problem persist. So its not the coils.

what about the ignition sensor in the distributor and the ignition control module?.....as i said in my original reply all 3 ignition components should be checked for problems when exposed to high heat.....

cliff