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Fuel lift pump Vs Primary fuel filter height

CaptnNero

Accelerant
I recently had a problem getting all of the air out of the fuel system :boohoo: for the engine to run reliably after cleaning the fuel tank and replacing the filters. It would run for a while and then stall out after a power drop.

When I got a mechanic to look at it, he turned the lift pump on and immediately said that the problem was with the lift pump. He also commented that having the lift pump mounted higher than the primary filter was not a good thing :rolleyes: . He used the hand priming pump on the top of the Racor filter for quite a while and was able to clear air from the system. Then it started and ran fine within about 30 seconds. Now I know the proper way to prime the system after watching him :egrin: .

I am looking into rearranging the lift pump and the primary filter so that the lift pump will actually be a little lower than the primary filter. The problem seems to be that air still in the system can more easily collect in the lift pump and airlock it when it is higher than the primary filter.

Has anyone else had an issue like this or ideas on it ?

-- neal
'88 E34 KOKOMO
 
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cawinter

Member III
My experience

Neal,

I can confirm occasional difficulty to prime the system. We do this a few times during various sailing classes, and I have always found that properly filling the RACOR to the point of diesel coming out of the vent hole is critical. I then just run the Facet with open bypass valve to bleed. Very rarely did I also bleed at the top of the secondary filter but normally that is not necessary.

It is very important for me to properly glow (20-30 seconds). That seems to be more than others have to do for a cold engine.

I assume we have the same setup.

Chris
E34 #267 1988
 

Shadowfax

Member III
In all the fuel filter changes I've done over the years on my M 25 XP, I have always found that running the bleeder for a couple of minutes then starting the engine with the bleeder still open was all that was necessary.

One thing I have noticed is when changing the Racor filter you must make certain that there is a complete seal between the bowl and filter body, or air will get into the system.
 

Tom Metzger

Sustaining Partner
I agree with Paul on this one. On my E-34 the pump and the Racor filter are close to the same level. I suspect the pump has enough guts to pull the fuel quite a bit higher than the engine compartment. After changing filters I don't bother filling either filter as the pump does it quickly with the bleed bypass open.
 

CaptnNero

Accelerant
More glow is better

This is my third boat with a 1988 Universal. When I bought the first one the seller told me to hit the glow button for 10 seconds. After a half season of sometimes long cranking, I actually read the Universal manual and it said "20-30 seconds". That made a big difference so I always wait 25 seconds even when other boaters on board have already said "That's long enough", unless of course the engine is already hot.

Incidentally, the first Universal had the same undersized starter solenoid wire as the Ericsons. We had an engine survey done and the mechanic tipped me off to that one.

Next time I'll try leaving the bypass open for a while after the primary has been bled.

-- neal

cawinter said:
Neal,

I can confirm occasional difficulty to prime the system. We do this a few times during various sailing classes, and I have always found that properly filling the RACOR to the point of diesel coming out of the vent hole is critical. I then just run the Facet with open bypass valve to bleed. Very rarely did I also bleed at the top of the secondary filter but normally that is not necessary.

It is very important for me to properly glow (20-30 seconds). That seems to be more than others have to do for a cold engine.

I assume we have the same setup.

Chris
E34 #267 1988
 
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CaptnNero

Accelerant
1 psi per two feet

I believe the ballpark figure is 1 psi will get you about two feet, and the Facet is at least 3 or 4 psi if not more, so it should pull several feet, well up to the cabin top.

The point the mechanic was making is that having the pump higher than the filter means that air can migrate to the pump and airlock it, after which it won't pull at all.

It interesting that you're able to prime using the bypass without even filling the filters. I may try that first next time.

-- neal

Tom Metzger said:
I agree with Paul on this one. On my E-34 the pump and the Racor filter are close to the same level. I suspect the pump has enough guts to pull the fuel quite a bit higher than the engine compartment. After changing filters I don't bother filling either filter as the pump does it quickly with the bleed bypass open.
 

CaptnNero

Accelerant
Bad news, good news

First, the bad news. After feeling good about how to prime the fuel system, the engine conked out again Sunday morning after a few hours of running since it's last problem. Once again the fuel lift pump was air locked, with the tell-tale fast cycling.

Now, the good news. When trying to bleed and prime the system again, the top of the bleed screw on top of the Racor primary filter came off in my hand ! It was made of nylon and had actually been glued before. Now at last I had a source for the tiny amounts of air that were leaking into the system but eventually stopping the pump after hours of run time.

I was planning on putting in a dual filter system anyway so I went to the marina boat store and bought a new one like the old one. Surprise, the new model is the same except the bleed screw is metal instead of nylon. It was easy to swap the new one in and I also put some thread sealant on the few non-flared fittings between the lift pump and the tank.

It's run another hour or two since the repair so I'll just have to see how it goes over time.

-- neal
 
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footrope

Contributing Partner
Blogs Author
Plastic Racor bleed fittings

Great news, Neal. Good to hear your mystery is probably solved. The last time I changed the fuel filters on my E38, the hexagonal head of the plastic Racor bleed screw broke off. It was late on a Sunday afternoon and that really p----d me off.

This is obviously a common problem and the heat of the engine compartment location probably contributes to the failure. Luckily, I was able to retrieve the threaded piece without removing the filter housing from the engine compartment wall.

Replacement bleed screws are brass and include the o-ring. They are probably available wherever Racor supplies are sold. Fisheries Supply in Seattle has plenty of them and I would advise that everyone make that a routine replacement task next time you buy filters.

Best of luck on your next engine run!
 

CaptnNero

Accelerant
Well I'm sure glad that you didn't just glue it back on and sell it to some poor unfortunate sailor. :egrin:

I'll have to check in Annapolis for the brass part before I install the old filter system in parallel. I saw it on the web for $5 but I don't remember where now.

Thanks for the validation.

-- neal

footrope said:
Great news, Neal. Good to hear your mystery is probably solved. The last time I changed the fuel filters on my E38, the hexagonal head of the plastic Racor bleed screw broke off. It was late on a Sunday afternoon and that really p----d me off.

This is obviously a common problem and the heat of the engine compartment location probably contributes to the failure. Luckily, I was able to retrieve the threaded piece without removing the filter housing from the engine compartment wall.

Replacement bleed screws are brass and include the o-ring. They are probably available wherever Racor supplies are sold. Fisheries Supply in Seattle has plenty of them and I would advise that everyone make that a routine replacement task next time you buy filters.

Best of luck on your next engine run!
 
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