Prime new mechanical fuel pump
08-02-2021 | 11:02 PM
#1
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Prime new mechanical fuel pump
Evening folks - My motor has been idle for over a year with a new fuel pump. What do I need to do to prim this pump? Cranking it doesn't pull any fuel from the tank in the short period it's cranking.is there something i'm missing?
Mercruiser 3.0 with mechanical fuel pump. Thanks in advance.
Mercruiser 3.0 with mechanical fuel pump. Thanks in advance.
08-03-2021 | 01:29 AM
#2
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From: Omaha/LOTO
First you had no spark and now you have no fuel??? You should not have to do anything but turn the key for about 20-30 seconds
Did you install a new water sep filter?? Did you not start it after installing a new fuel pump??
Did you install a new water sep filter?? Did you not start it after installing a new fuel pump??
Last edited by Griff; 08-03-2021 at 01:36 AM.
08-03-2021 | 05:11 AM
#3
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From: Lake Winnipesaukee, NH
Did you install the pump yourself? Did this engine have a mech pump previously?
There should have been some pump arm spring pressure to overcome when bolting the pump to the engine. If not check that you have the right pump for the pushrod and right rod for the pump.
Reason I ask is I have seen small blocks WITH a pump boss that actually can't use a manual pump because they aren't drilled for a mechanical pump. I imagine they just saved the castings even though they stopped using the mech pump.
And if your engine started life with an electric pump it usually won't be able to retrofit to mechanical. Also if it was originally electric you can't change back because the cam should not have a pump lobe.
Now
You have to have all suction joints sealed and perfect fuel line for the pump's suction to bring the fuel.
And DO NOT use thread sealant tape, only the smallest amount of brush on sealant. Place the sealant well back from the actual fuel path on the threads. If any gets in the fuel you are SOL.
I have always just replaced the lines on my boats because I buy boats that are old. But even for a 10 year boat it's a good idea.
I recommend removing the anti siphon valve that's at the top of the fuel tank and verifying that it is clear too. It only takes a moment to unscrew it and exercise the check ball while running some carb cleaner or gasoline through it.
It's there and accessible, you ought to verify it is good.
There should have been some pump arm spring pressure to overcome when bolting the pump to the engine. If not check that you have the right pump for the pushrod and right rod for the pump.
Reason I ask is I have seen small blocks WITH a pump boss that actually can't use a manual pump because they aren't drilled for a mechanical pump. I imagine they just saved the castings even though they stopped using the mech pump.
And if your engine started life with an electric pump it usually won't be able to retrofit to mechanical. Also if it was originally electric you can't change back because the cam should not have a pump lobe.
Now
You have to have all suction joints sealed and perfect fuel line for the pump's suction to bring the fuel.
And DO NOT use thread sealant tape, only the smallest amount of brush on sealant. Place the sealant well back from the actual fuel path on the threads. If any gets in the fuel you are SOL.
I have always just replaced the lines on my boats because I buy boats that are old. But even for a 10 year boat it's a good idea.
I recommend removing the anti siphon valve that's at the top of the fuel tank and verifying that it is clear too. It only takes a moment to unscrew it and exercise the check ball while running some carb cleaner or gasoline through it.
It's there and accessible, you ought to verify it is good.
08-03-2021 | 10:18 AM
#4
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Yes, working through one challenge at a time.
Negative - there was not fuel water seperator on the engine and not one outlined in the service manual.
No, as you mentioned before I was being challenged with not having a spark.
I believe i replaced this with a like for like. A carter mechanical pump. The new one looks identical to the old one. Old one had a paper filter, the new one has a stone filter. That's the only difference.I'll remove the new filter and double check for the spring tension against the mechanical arm.
All good advice, I replaced the anti siphon valve and verified it was clear, so good to go there. You mentioned a brush on sealant. What do you recommend?
Negative - there was not fuel water seperator on the engine and not one outlined in the service manual.
No, as you mentioned before I was being challenged with not having a spark.
Did you install the pump yourself? Did this engine have a mech pump previously?
There should have been some pump arm spring pressure to overcome when bolting the pump to the engine. If not check that you have the right pump for the pushrod and right rod for the pump.
Reason I ask is I have seen small blocks WITH a pump boss that actually can't use a manual pump because they aren't drilled for a mechanical pump. I imagine they just saved the castings even though they stopped using the mech pump.
And if your engine started life with an electric pump it usually won't be able to retrofit to mechanical. Also if it was originally electric you can't change back because the cam should not have a pump lobe.
There should have been some pump arm spring pressure to overcome when bolting the pump to the engine. If not check that you have the right pump for the pushrod and right rod for the pump.
Reason I ask is I have seen small blocks WITH a pump boss that actually can't use a manual pump because they aren't drilled for a mechanical pump. I imagine they just saved the castings even though they stopped using the mech pump.
And if your engine started life with an electric pump it usually won't be able to retrofit to mechanical. Also if it was originally electric you can't change back because the cam should not have a pump lobe.
You have to have all suction joints sealed and perfect fuel line for the pump's suction to bring the fuel.
And DO NOT use thread sealant tape, only the smallest amount of brush on sealant. Place the sealant well back from the actual fuel path on the threads. If any gets in the fuel you are SOL.
I have always just replaced the lines on my boats because I buy boats that are old. But even for a 10 year boat it's a good idea.
I recommend removing the anti siphon valve that's at the top of the fuel tank and verifying that it is clear too. It only takes a moment to unscrew it and exercise the check ball while running some carb cleaner or gasoline through it.
It's there and accessible, you ought to verify it is good.
And DO NOT use thread sealant tape, only the smallest amount of brush on sealant. Place the sealant well back from the actual fuel path on the threads. If any gets in the fuel you are SOL.
I have always just replaced the lines on my boats because I buy boats that are old. But even for a 10 year boat it's a good idea.
I recommend removing the anti siphon valve that's at the top of the fuel tank and verifying that it is clear too. It only takes a moment to unscrew it and exercise the check ball while running some carb cleaner or gasoline through it.
It's there and accessible, you ought to verify it is good.
