2000 500EFI - Fuel Issues - need expert advice if possible
 

I have 2 500EFI in a 2000 Formula Fastech with 200 hrs on them

Both motors 'act' like they are vapor locking from time to time. I have just accepted this as a normal (painful) fact of life that i must bleed the motors to get them moving from time to time.

Both have only the electric fuel pumps, no booster.

hooked up a pressure gauge to the bleeder schrader valve the other day and opened up the 'bleed' valve on the pressure gauge to let the fuel flow through the clear tubing.

I see that there is significant air in the clear tube as it flows out of the bleeder valve even after draining enough fuel that it should have emptied the whole fuel system, so am wondering if something else might be happening causing the symptoms of vapor lock.

Max fuel pressure was 38 on stbd and 42 on port so this doesnt seem too out of the ordinary, but the air in the fuel line seems like it could be a contributing factor to vapor lock.

Also ran a vacuum gauge just before the port side fuel filter to see if i had a leak in the suction side and the suction seemed fine. Read 2-3#s if i remember right.

Has anyone seen this before? Could bad fuel pumps cause air to be introduced or is something else going on?

Thanks,

Jim

ttt? Can anyone help me to determine what my next testing steps might be? Any experience with a similar issue?

Aftermarket efi fuel pump with and adjustable regulator and your done. Best thing I ever did with my 500efi.

Thx Black Baja. Can you give any details? Was the aftermarket pump a booster pump or an entirely new fuel system? What brand/model? About how much did the changeover cost?

Why did you need to do that? Just wondering because my 500EFI's are bone stock and I don't have issues.

What issue were you having? Only thing I have had to do fuel system was replace one of the pumps. That was a PITA!

My 500EFIs are both stock as well. forgot to mention that.

my buddy has a 1999 382 500efi blue motors same kind of symptoms, ended up going to premium fuel to get it to stop .Especially on hot days

That fuel system can hold a bunch of air. Since the fuel is pre-regulated, any air in the fuel rails can only get out by going through the injectors. It will take some time to get all of the air out. Put the pressure gauge on the rail and run the engine for a bit. You may even want to run it on the lake with someone monitoring the gauge. See if there are any fluctuations, pressure drops, etc. Do that for both engines.
If it had a leak on the suction side, it would probably not want to even pick up the fuel. Those pumps DO NOT have much in the way of suction. They are made to push fuel. So, I don't think that is your problem.
Eddie

Just for schits and giggles, has anyone tried an extended pick up fuel water separator head ? I know someone makes it.

Thanks Eddie, Since the boat seems to run perfectly when underway and i only see issues at starting time should i focus my efforts on pre-start fuel pressure or do you think that if i check in-operation fuel pressures that will tell me something about the fuel pumps? How large of a variation in that pressure would be acceptable underway?

I ran about a quart of fuel through by just turning the key to accessory position and back off a bunch of times and was still getting air in the fuel that was delivered when the fuel was tapped at the fuel rail.

a. Fuel temperature (at the engine’s fuel inlet fitting) and the amount of vacuum
required by the fuel pump to draw the fuel from the boat’s fuel tank can contribute
to vapor locking.
Mercury MerCruiser’s maximum engine fuel temperature specification that became
effective January 1, 1996 is:
Under the hottest outside air temperature condition that the boat will be operated
in, the temperature of the fuel being supplied to the engine shall not exceed 110o F
(43o C) at any location between the fuel tank and the engine’s fuel pump.
Mercury MerCruiser’s specification for the maximum vacuum measured at the fuel
inlet of any MerCruiser engine is:
2 in. Hg (7 kPa) maximum at idle rpm, 3000, full throttle and back at idle rpm.
Use an accurate digital vacuum gauge that reads in either in. Hg (inches of mercury)
or (kPa) to check this specification. Common vacuum gauges to check an engine
intake manifold vacuum are not accurate enough to make this type of measurement.
b. Reducing the temperature and maximum vacuum of the fuel being supplied to the
engine will help reduce vapor locking problems.
NOTE: Carbureted and EFI/MPI with VST models only: The Water Separating Fuel Filter
can be removed from the engine to a lower, cooler location. Use a Coast Guard approved
fuel line between the filter and the fuel pump

If you are saying this is only a preliminary starting issue then what i would do is hook up a psi gauge on the fuel rail...prime the system up and see if it hold the psi...if its dropping off then you either have a leaky injector/s or possibly a bad fuel pressure regulator.....

Yes this seems to only be a starting issue. I did fuel pressure measurements with the appropriate injector gauge and all seemed relatively normal. The thing im not sure of is that i was getting a lot of air in the bleed line when i drew fuel off of the gauge at the fuel rail. That seems like a problem. Seems like no matter how many times i cycled the fuel pump to move air out of the system i was still getting a good amount of large air bubbles off of that bleed line.

Thanks SB for the tech information. I already measured the vacuum and it was about 2in Hg. so that seems normal

Has anyone relocated their Fuel Filter lower in their bilge? How did you do it? Any special brackets you used? Did it help with vapor lock?

I added a Procharger to mine. Just did a complete Aeromotive system. Burnt up two pumps in two weeks. After that I learned the right way to plumb an Aeromotive pump and had many trouble free hours. I did the same thing on a customers 500's that was having fuel pump issues. Changed thwm over to Aeromotive pumps and regulators with returns. Also put larger pickups in the tanks. Setup was trouble free for years. And what Mercury gets for a new pump I would just convert them...

Im not talking about fuel pressure while running....when you first energize the system the pump should turn on for a few seconds and pressurize the fuel rail to a set amount for starting...although im not 100% sure if the 500EFI's do this as they do have a mechanical pump as well.....either way fuel pressure should hold steady before starting...and should be holding after running too....if its dropping then you have a leak in the system and its bleeding down.....my guess is the regulator....but it could just as easily be an injector dripping.
I would take the injectors out and have them cleaned and balanced....Talk to BUP about that ;)
And since the manifold would be apart at this point just replace the regulator while in there. :)

Look here at part#19
http://www.mercruiserparts.com/bam/s...31335/4889/110

Also just out of curiosity.....your not getting an "fuel sheen" on the water behind the boat as it runs do you?? That to me would signal that the fuel cooler has a leak and dumping fuel into the raw water system and could be your leaking point...

Here in texas, in the summer , the carbed direct drive ski boat guys seem to get the vapor lock blues first.
Dumping ice water on the intake and fuel lines to get it started again really kills thier mojo.
The local marina fuel at double the cost of road side pump gas is much better and swaps to winter fuel better. Todays ethanol gas is worse than ever. Fuel under vacuum near hot exhaust power steering pumps ect will start to boil almost at ambient if its hot enough outside. Next time it happens hose down the fuel system with ice water all the way to where the lines go to the tank or undsr the floor and see if it makes a instant difference

Merc recommends 2 hg MAX for Vacuum testing if you are higher than that - you possible can have a restriction(s) or air leaking into the fuel system or even tired fuel pumps.

If your fuel pressure will not stay steady - you have a restriction or a voltage problem or a fuel regulator problem

if you have fuel pressure that drops - that can be weak fuel pumps or leaks or o ring gasket seal at the injectors or the injector(s).

And yes I do test and flow test injectors and clean them professionally. , 8 years coming up on and only for marine apps.

It is becoming recommended maintenance by the marine OEMs to have the injectors looked at every 4 to 7 years or sooner if fuel issues can not be traced down. And if you have water in your fuel and or rust especially rusted internal fuel lines./ fuel rails.. Actually on 496's that is common more than you think (internal corrosion in the fuel rails) . Believe me when I say this. I see it almost weekly during boating months.

Also another big cause for Vapor Lock is RVP ( Reid Vapor Pressure ) of the fuel. This also is a big problem as well. Search for it up here as I have made many posts about. Years ago all the OEM marine schools would talk about this all the time --- RVP.

Instead of writing this out read the SB from Mercruiser. Vapor lock has been a problem in boats way before 1999 per Service Bulletin aka SB.

http://www.boatfix.com/merc/Bullet/99/99_07.pdf

And basically the same info

https://www.perfprotech.com/blog/art...ser-vapor-lock

Engine compartment temps matter --- incoming air and venting especially venting heat soak after engine shut down. Running the blower can help as well and proper cooling of your engine(s)

Have tried idling, keeping the hatch open, running blower at all times. None have helped. Just ordered the merc boost pump kit. Every post i have seen where someone installed, that seemed to have solved all of their issues.

I will repost here with my results so that others have another data point to go from.

I assume that installing the booster pump increases the pressure on the supply side to the high pressure pump (through the water seperator) to prevent the fuel from boiling At a minimum it should put a pump in a spot where non-boiled fuel can be picked up and pumped to prime the high pressure pump in the case that vapor lock does occur.

I am keeping my fingers crossed... I hope the kit comes with instructions on how to install. I have not been able to find any instructions anywhere online.

also pre filter 100 microns before the boost pump ----- if you ordered the correct Merc kit then it will come with the boost pump filter ( metal canister filter) . Also cushion clamp that boost pump filter at the installed location.

Thanks BUP, yes the kit appears to come with pump, bracket, filter, filter clamp, electrical connections, plumbing fittings etc.

From what i can tell the bracket for the boost pump itself somehow piggybacks onto the mounting bolts for the fuel/water seperator. I assume the filter can be mounted down low in the bilge on a stringer somewhere.

Here is the data I collected on the fuel pumps. Motors only have 200 hrs

Stbd engine

Just key no motor running. 43 with pump running
After 30 seconds 37psi
After 5 minutes 34psi

With motor running at idle. 37-38
At 3000rpm. 34psi

Port engine

ust key no motor running 44.5
with pump running
After 30 seconds 39
After 5 minutes 34

With motor running at idle. 39
At 3000rpm. 37

Does this look ok?

anyone?

I would replace the fuel pumps and not install the boost pumps. The 500 EFI fuel for system is usually very problem free. I have solved the exact problem you describe by replacing pumps on three different applications over the years. Not really sure why but all were intermittent hot no start and a new pump fixed it. Boost pump makes sense and is probably useful but not sure it's necessary.

I had the same issue with vapor locking after converting from the VST system to the cool fuel system. Ordered the boost pump kit from Merc, installed it and have never had the issue again. That was 9 years ago. Still running on the same cool fuel pump and boost pump with no issues, fwiw..

Thx for the confirmation tgorbett.

Was it a 500EFI that you installed the merc vapor lock kit on? Looking at the instructions they say that the kit is for all Mercruiser V6 and V8 engines. Do you think there will be any issue with installing this on a Mercury Racing 500EFI?

Where are you at anyway ? We are out of vapor lock season here for the most part.
Even the 377 scorpion that is in a sealed box (long story) has been behaving

Meybe you got the early flip to winter blend fuel

Just as a follow up in case anyone else is having a similar issue and does a search:

I installed the merc booster pump kit in my boat over the winter. In the past for the first couple of runs of the season i would see 1-2 vapor lock conditions.

After booster pump installs, I have not seen any vapor lock conditions. Boat has been running great. Booster pumps appear to have solved the problem.

Thanks all

Just as a follow up in case anyone else is having a similar issue and does a search:

I installed the merc booster pump kit in my boat over the winter. In the past for the first couple of runs of the season i would see 1-2 vapor lock conditions.

After booster pump installs, I have not seen any vapor lock conditions. Boat has been running great. Booster pumps appear to have solved the problem.

Thanks all

There is a change out adaptor for this as well. Also GLM offers something if I recall correctly. -