5.7 mercruiser wont start

[swampy2646]

Re: 5.7 mercruiser wont start

havent found out why its not sparking, every thing points to the dist. sensor, but when i put one in ,same results. maybe my buddy hooked it up wrong, i dont know, i think im gonna get another one and try it again. i put the old one back when it didnt start.

 

[deadstick]

Re: 5.7 mercruiser wont start

okay, can you run down what you have replaced?have you checked the + current going to your coil & module?

 

[swampy2646]

Re: 5.7 mercruiser wont start

if you read the first thread it tells you everything i tried, are you familiar with the flow chart on the TB ignition, for some reason im still stuck on it being the sensor. off to marina now, i'll post any results

 

[deadstick]

Re: 5.7 mercruiser wont start

\maybe my buddy hooked it up wrong, i dont know, i think im gonna get another one and try it again. i put the old one back when it didnt start.

i have read over all of the thread. i looked over the flow chart. in this post you say that you put the old one back on when it didnt start. did you check the fire with the new one or did you just try and crank it? the engine could be flooded (the reason for not starting).

you may have done this but just trying to double check.

 

[swampy2646]

Re: 5.7 mercruiser wont start

ok, prong one is solved, i re did the sensor and i now have spark. now comes prong 2....... the gas is pouring out of the top of the carb. like crazy, i already changed the mech. fuel pump last week and it actually got worse. i have a crossover system with two tanks, i can move the "T" to just slightly open position and she runs ok. but obviously there is a fuel pressure issue(way too much). havent put a pressure gauge on it yet. when i shut it down gas is so pressurized, i can hear and see it filling up th e carb until it subsides. my vents seem to be ok. anybody got any ideas????? Pete

 

[deadstick]

Re: 5.7 mercruiser wont start

swampy, im glad you go the fire issue straight. i would think a mech. fuel pump would not cause more pressure than the float could hold back. sounds like a bad carb. quadrajet carbs are a lil trickey. did you rebuild the carb? when you built the motor did you keep this carb sitting upright, never turning it upside down.

 

[swampy2646]

Re: 5.7 mercruiser wont start

I actually have 2 q-jets, the orig.one re-built and bench tested at 10 psi. This problem happens with both carbs and 2 fuel pumps!!!

 

[deadstick]

Re: 5.7 mercruiser wont start

you have stumped me. when you figure it out let us know.

 

[swampy2646]

Re: 5.7 mercruiser wont start

will do.

 

[swampy2646]

Re: 5.7 mercruiser wont start

just did a fuel flow test, the thing pumped 1/2 gallon of gas in 10 seconds,probally 10 times more than specs. its a brand new pump, what gives???

 

[deadstick]

Re: 5.7 mercruiser wont start

swampy, can you give me the part # for the pump.

i may be wrong, but im not sure on how you checked the flow. you need to check presure with a gauge. i think they will free flow with out be hooked to somthing to restrict the flow...

puzzling

 

[SeanMcl]

Re: 5.7 mercruiser wont start

just did a fuel flow test, the thing pumped 1/2 gallon of gas in 10 seconds,probally 10 times more than specs. its a brand new pump, what gives???

I'd say you have the wrong fuel pump in there. Find another source of reference for part numbers. Another brand of manual, a couple different online catalogs, call a different shop and ask, punch in the part number of the one you bought and see if it comes up as matching your I/O, etc.

I wonder if you have a high pressure pump for a fuel injected motor, when you need a low pressure pump for a carbed version.

 

[deadstick]

Re: 5.7 mercruiser wont start

I wonder if you have a high pressure pump for a fuel injected motor, when you need a low pressure pump for a carbed version.

very good point!

 

[swampy2646]

Re: 5.7 mercruiser wont start

the merc part # matched the one on the description sheet, but that was just on the box. could it have been switched or something, i dont know, the box was taped shut. i'm rigging a guage now to do a pressure test tomorrow , Thanks, Pete

 

[swampy2646]

Re: 5.7 mercruiser wont start

read thread "excessive fuel pressure"