engine wont idle for more than a few minutes

[imported_rosco]

Re: engine wont idle for more than a few minutes

well, back at it.

mercruiser system is definatly out. looking at around 2k to replace the whole system with a newer system that usses a water cooled bowl, and over 1600 to replace all the suspect parts on mine. not to mention the 4 to 6 weeks wait for parts.

crusader usses a complete bolt on system that looks ideal, but they dont want to help. blew me off with 3 to 4 months wait and will not warentee it on a mercruiser engine as if there is a differance between their gm block and anyone elses.

down to after market or scrap the EFI and go with a carb.

honestly, it would be faster and cheaper to scrap the system and buy an intake and carburator. it really shouldnt be this time consuming or expensine to replace a fuel delivery system. gona make one last stand before i strip it off and sell the whole system on e-bay minus the fuel pump.

the problem with aftermarket. connections.

first, i need a low pressure pump to feed the high pressure pump. no bigge. dozens of them. i setteled on the Holly Red Pump. problem is, all the connectors are 3/8 npt on the pump, and all my lines are 1/2 npt. on the entire system.

need to find 2 - 3/8 to 1/2 inch adaptors or have 2 fuel lines made somewhere. one from the fuel filter to the pump and one from the low pressure pump to the high pressure pump.

no biggie.

the high pressure pump is the problem. it needs to flow LESS fuel than the low pressure pump or it will starve for fuel.

all, and i mean ALL available high pressure pumps have metric fittings.

i setteled on the Aeromotive Tsunami pump. 60 GPH at 45 PSI. perfect match for the Holly Red pump with its 67 to 97 GPH flow rate.

but it has an -8AN inlet and a -6AN outlet. AND i still need a regulator.

there was a chance of finding a 3/8 -1/2 adaptor, there is no chance in hell of finding a metric to standard adaptor in the sizes i need.

need to have all new lines made from the fuel filter and on. more time. bah.

toss in there will be no provision for solving vapor lock problems......really getting on my nerves. and if Holly is overstating the flow rate, the aeromotive pump will starve and either vapor lock for sure, or overheat and fly apart.

pros-
1. cost. the entire system will be less than 600 bucks complete.
2. serviceability. replacing the pumps after its complete in the event of a future failure wil be 2 days tops with fed-x.
3. diagnosing problems. the system is simple. it is either the low pressure pump or high pressure pump or filter. all fo which can be checked with a pressure gage.

cons,
1. no mechanic will ever touch my engine again with a piece meal system on it. i will be the only mechanic.
2. resale. probably not going to inspire confidence when a prospective buyer looks at it.
3. the unknown. have no friggin idea if it will work. will it vapor lock from varing flow rates? will it over heat? will it leak? in how many places? what will i attach it too?

the things that make life an adventure........
2

 

[imported_rosco]

Re: engine wont idle for more than a few minutes

HAH,

just figured out NPT is pipe thread, and AN is flare, not metric.

connections will be a snap. infact, only hose i think i will need to make is a return line from the fuel rail to the tank. it currently runs back to the fuel bowl.

thinking about running 2 lines from the tank to the fuel filter too to reduce possible restriction from the increased flow.

so mabe 2 lines. just need a place to mount them now. im pretty sure i can mount the low pressure pump to where the mechanical pump is now, on top of a block off plate.

no clue where to mount the high pressure hose. might have to have a bracket made. needs to be someplace away from the exhaust, but close to the back of the block so the hose to the rail is as short as possible. need a regualtor too, but they are not hard to find.

 

[imported_rosco]

Re: engine wont idle for more than a few minutes

BAH,

all holly pumps are gravity feed. IE, they will not pull fuel through a anti-siphon valve and fuel filter.

i asked them how they could sell a "marine" pump if all boats must have anti-siphon valves and a filter and their pump wont work with them? no reponse.

well, looks like i might have to use a mechanical pump to pull fuel to the high pressure pump, like my current system.

gona try something first though. going to run 2 lines from the fuel tank into a y then into the filter. then going to plug up the return port on the vst fuel bowl and run the return line into the gas tank.

forseable problem, mechanical pump will not be able to keep up with high volume pump and run dry. but mabe mercruiser had the forsight to use a mechanical pump with a higher flow rate than the high pressure pump.

if the system doesnt run dry, it will effectivly eliminate any fuel heating problem as the source of the problem.

if the system does run dry, i can try a high volume after market mechanical pump, adn thus the need for 2 fuel feed lines.

 

[imported_rosco]

Re: engine wont idle for more than a few minutes

success....of a sorts.

i replaced the fuel filter bracket with one with 3/8 fittings instead of the factory one with 1/4 fittings. you never know.

then i plugged up the return port on the VST bowl, and ran the return line from the fuel rail to the tank as opposed to back into the VST tank. no more recirculating hot fuel back to the high pressure pump.

cranked her up and she hasnt stoped running yet. over an hour so far.

still not satisfied however. the boat will not reach 180 degrees. it is holding fast at 170. might have something to do with not burning hot fuel, i dont know. the problems start when it hits 180 degrees.

also, the high pressure pump could be on its way out, and thus, not working well with the hot fuel anymore where as a new one would. by eliminating the hot fuel, it may be less of a problem solved as a problem delayed.

well, gona drag my brother out into the bay for a hard test run and see what breaks.

either way, it is not time wasted. i have confirmed the factory high volume fuel pump will keep up without the return flow from the high pressure pump. i have also routed the return line to the tank, which would have to be done with an aftermarket pump anyway.

if we get towed back by seatow, all i have left to do is unbolt the entire VST system, and make a bracket and mount any dependable aftermarket high pressure pump with some fitting adaptors. only other thing that i might have to do, is replace the factory mechanical pump with an aftermarket bolt on that flows more fuel. plenty of them out there.

sooo, i know im atleast half done. mabe completly done if the high pressure pump holds up to a beat down at WOT under a load.

i understand now why boat manufacturers do not return the overflow to the tank. if you ever get a leak in the return line, it will pump fuel into your belge untill you shut off the motor. there is no way to check valve return flow like you can with the suction side with an anti-siphon valve. it just cant be done.

outboards get away with it because a leak will just sprey fuel all over the transom. no explosion. fire mabe, but no big bang.

if everything checks out, ill call a hydrolic company that makes high pressure lines for heavy equipment and have the entire return line made with 1000 PSI fuel line with screw on fittings at both ends. it is as safe as i can make it without pumping hot fuel back to the high pressure pump.

final annalysis, boats shoud not have fuel injection systems at all. there is just no way to make them totally safe without compromising their effeciency. even with the factory system, you have a return line even if its only a couple feet long. if it starts leaking, the engine will keep running untill the engine compartmant explodes, or you shut off the engine. more than likely, the explosion will happen when the fuel gets high enough to activate the belge pump.

but, a high pressure line should make it as safe as it can be. you can get killed by a stinray snorkeling too.

 

[imported_rosco]

Re: engine wont idle for more than a few minutes

time for beer.

it works like a champ. ran it at WOT for a while then ideled around for a good 30 minutes or so, didnt stop untill i shut it off.

one little kink with rerouting the fuel line though. when you turn on the key, the high pressure pump runs for 3 seconds and pretty much sucks the VST tank dry now that the overflow is going back into the tank. had to disconnect the high pressure pump and turn it over for a few seconds to fill the tank, then reconnect it to get it started at the dock,

but it started fine when i ran it to flush it.

if it becomes a consistant problem, 2 ways to fix it. disable the relay that runs the pump pryor to starting. then it would start like a carb engine, with a little bit of turning over before it fires up. other way is to replace the mechanical pump with an electric pump so it fills the VST when the key is turned on.

reguardless, it wont stop me from going out and it is something i can fix at my leasure.

end result of my origonal problem:

vapor lock. the recirculated fuel in the VST tank was heating up to the point of boiling, creating air in the tank, causing the high pressure pump to loose pressure.

conclusion:

mercruiser couldnt design their way out of a wet paper bag. soo many ways to adress this set up that would have worked better. 1. run the return back into the tank. 2. use a 2 speed high pressure pump so at idle, the return flow is cut in half or less allowing more fresh, cool fuel into the tank from the mechanical pump. 3. run the return fuel farther back in the system, like mabe into the fuel filter so it has some time to cool before returining to the VST. 4. copy volvo pentas design. 5. copy crusaders design. 6. run the return line through an oil cooler tube then back into the VST.

mercruisers solution? water cool the VST tank. doesnt do crap about recirculating hot fuel, but keeps it from boiling atleast. a band aid for a power robbing problem.

my pump may still be bad, i dont know. but i do know, when it finally does fail, it wont be vapor lock or hot fuel. and when it does go, ill toss it along with the entire VST and bolt on an after market pump and either disable the precharge relay or bolt on an electric low pressure pump if i can find one that will pull fuel as well as push.

i may have fixed my problem, or i may have bought myself some time. the only thing i know for sure is i learned alot of crap i would have gladly paid someone else to do if i could find a mechanic worth a crap. kind of a bitter sweet life lesson.