Hard to start after running......

[Captain Vis]

1995 OMC Cobra 5.8 Litre V8 EFI Multiport <br />Changed the plugs last week and she runs great, no overheating, good acceleration, I am very happy with the performance. One problem...after running for about 30 minutes at normal speed, I find it hard to start the engine again after 5-10 minutes (with the blower on). It will start,but only after I give the throttle a lot of gas. Then it will idle erratically for about 15 seconds and smooth out. I have yet to change the cap and rotor...could that be the problem or ???????

 

[Spidybot]

Re: Hard to start after running......

Think the buzzword here is 'vapor lock'.<br /><br />Due to the heat from the engine and in the engine compartment in general, fuel vaporises inside the fuel system. These passages of 'air' makes it hard or impossible for the system to supply fuel to the engine. Some manufaturers fit heat shields (like on cars) to protect the fuel components from the heat. <br /><br />At least move fuel lines away from hot spots.

 

[akriverrat]

Re: Hard to start after running......

flooding? to start a hot flooded engine be sure choke is open, open throttle fully, wait 5 minutes for excess gas to evaporate, start engine and reduce throttle as rpms rise and engine smooths out from overrich condition. could just be the choke needs adjusting.

 

[Captain Vis]

Re: Hard to start after running......

It's fuel injected, no carb....

 

[akriverrat]

Re: Hard to start after running......

sometimes i amaze myself with how i can miss things. sorry. http://www.marinemechanic.com/omc/no-4138.htm is the only thing i could find that has any bearing on the situation.

 

[peter_mayers]

Re: Hard to start after running......

Hi Captain Vis ,<br />Did you get it fixed? I have identical problem on mu 5.0 multiport.

 

[snapperbait]

Re: Hard to start after running......

I'd venture two guesses.. #1 Idle air bypass solenoid faulty.. (sometimes they just get clogged up and need a cleaning)<br /><br />#2 Base ignition timing is'nt correct...

 

[peter_mayers]

Re: Hard to start after running......

I thought that too, but If I just shut off and restart within a minute is start fine. If it sits for 15 minutes or longer then I cannot start. If it was timing or valve it would have problems starting all the time, right?. This only happens when it sits hot for some time, any other time starts right up. Anyone else had that problem? What tools do I need to check fuel pressure? I had a similar problem on my car and it turned out to be faulty fuel pump. I do not know how the car experience translates to boats, but I cannot think of any other reason.<br />Do you guys have any other suggestions? I have the shop manual but they do not provide any troubleshooting. The shop manual says to go to the dealer, kind of ironic isn't it.

 

[McKenzie]

Re: Hard to start after running......

I think UU had it right when he said vapor lock. That would be the first thing i would try to eliminate. Install disposable clear fuel filter into the fuel system, preferably after the fuel pump and as near to the block as the fuel lines are. When the engine acts up, take a look at the filter, is there some gas with bubbles? That would tell you that it has vapor lock. If it is completely empty, that means that the fuel has completely flowed back into the tank. That will happen if there is a bad check valve at the tank, possibly the fuel pump is at fault, or there is a leak and air was allowed to displace the gas.

 

[peter_mayers]

Re: Hard to start after running......

Hey McKenzie;<br />This is a good idea. Do you know which filter will fit fuel line fittings on a 5.0 96 volvo penta? I will work on this over the weekend.<br />Thanks

 

[Captain Vis]

Re: Hard to start after running......

Ok here's the solution to the problem....two things. I replaced the anti-syphon valve ( they do wear out after 8 years) and now do the following. turn ignition on 10 secs. off 10 secs. on 6 secs. and start. It works every time. What it is doing is tricking the fuel pump timer. I only do this when I have been running hard or it is a very hot day. Other than that she's smooth as silk.........

 

[magster65]

Re: Hard to start after running......

Howdy. <br />What does tricking the fuel pump do? This is a good clue to the problem.

 

[Captain Vis]

Re: Hard to start after running......

What does tricking the fuel pump do?.......starts the engine.

 

[Dunaruna]

Re: Hard to start after running......

You will need to check your fuel pressure (in line gauge) to elimiate that as a cause, after shutting down, the fuel system should hold pressure for at least 30 min. You said that it runs rough for about 15 sec. after start up and then smooths out, sounds like a lose of pressure while engine is off. Pressure needs to build up before start - hence delay in starting. Runs rough for 15 sec. - could be a dribbling injector over fueling and causing a rich mixture at start up. The pressure relieve valve was my next line, but you beat me to it. "tricking' the pump only masks the problem.

 

[Dunaruna]

Re: Hard to start after running......

P.S. if fuel pressure is o/k (around 200kpa) then vapor isn't an issue.

 

[peter_mayers]

Re: Hard to start after running......

I got it fixed at a mechanic. The teperature sensor was bad. I guess it was thinking it is cold and floding the engine.