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Gen 6 502 mpi mag cold start

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Gen 6 502 mpi mag cold start

Old 06-08-2018, 12:26 PM
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Default Gen 6 502 mpi mag cold start

So engine has 500 hours, starts and runs great. Only issue is when starting cold or after engine off for more than an hour , it seems like it has to crank for 3 or 4 seconds before it fires up. After it starts , you can kill it and bump the key and it fires up. Has a vacuum style lift pump off the water pump to get fuel to the high pressure pump. I was thinking maybe it is leaking down and had considered replacing it with an electric low pressure pump. Ideas ?
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Old 06-08-2018, 01:25 PM
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Mine does the same thing but only when cold, which I kind of like because the oil gets around a tad before it lights off. I only have the cool fuel pump and no mechanical or electric low pressure

The mechanical pumps are good pumps so long as there working as designed. They can suck fuel and an electric is not to great in this area, it also sucks but just not as hard. If you have a sticking antisiphon valve the mechanical can take care of over coming the issue, electric not so much; but then again maybe you want to know if it has issues.

Being a 96 its probably cool fuel and not VST, don't know. Check your fuel pressure to see if it comes up to spec and when key is off, does it hold or fall off quickly. If it goes quick, could be injectors or regulator. If it goes slow my first guess would be regulator. Also check fuel pressure on the low side, it could be bleeding off
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Old 06-08-2018, 02:46 PM
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if its a gen 6 should be a cool fuel system check your fuel pressure at the rail as alldodge has suggested there should be a check valve at the fuel cell where your fuel line connects at the tank
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Old 06-08-2018, 02:50 PM
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check the pressure regulator vacuum hose.. often those regulators leak into the vacuum line.. pull the line off and see if its wet.
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Old 06-08-2018, 02:53 PM
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vacuum style lift pump what year is this engine?
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Old 06-08-2018, 04:47 PM
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Originally Posted by 232 View Post
vacuum style lift pump what year is this engine?
Well, I say that as it has a vacuum hose going to it , the regulator and the high pressure pump. It is a 96
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Old 06-08-2018, 05:09 PM
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Originally Posted by jryotas View Post
Well, I say that as it has a vacuum hose going to it ,
That's not a vacuum hose, its tubing which sends fuel to the intake IF (big if) the diaphragm ruptures. That said, most of the pumps do leak slightly after some many years, and therefore the gear lube in the pump body needs replaced yearly
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