Electronic fuel pump question on 91 Mercruiser 4.3/V6

[ASEAudie]

Hello everyone,

Question is; is the fuel pump supposed to cycle as soon as the key is turned to run position?
Just wondering if there is supposed to be a failsafe setup in case of emergency?
Next question; how to determine if this pump is Marine or Auto?

Thanks in advance...
Audie

 

[Failproof]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

If carbed, pump should not run untill key is in start position, or oil pressure has built. Unless it is aftermarket wired with a primer timer(3 to 5the second to prime bowls). Check pump for serial numbers or a sticker/stamp that says marine or uscg approved.

 

[ASEAudie]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

If carbed, pump should not run untill key is in start position, or oil pressure has built. Unless it is aftermarket wired with a primer timer(3 to 5the second to prime bowls). Check pump for serial numbers or a sticker/stamp that says marine or uscg approved.

That's what I thought; should only cycle when starter is cranking.
Obviously someone added this "Carter" brand automotive pump, it has surface rust on body and mounting hardware, and no marine approved ID anywhere.

Thanks for the response, oh and uh, it is carbed.
Audie

 

[achris]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

91 was only ever carbed (the question is 2 bbl or 4, and even that's irrelevant) and only with a mechanical pump. So, an electric is someones' botch-up.... And it sounds like there's no oil pressure switch in the circuit... :facepalm:

 

[Don S]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

Here is how it is supposed to be wired in using an oil pressure switch, and the purple yellow wire going to the starter.

Just click on the thumbnail

 

[achris]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

Here is how it is supposed to be wired in using an oil pressure switch, and the purple yellow wire going to the starter.

Just click on the thumbnail

View attachment 152227

Do you have thousands of these little drawings tucked away ready for almost any question anybody could come up with???

 

[Don S]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

Do you have thousands of these little drawings tucked away ready for almost any question anybody could come up with???

You wouldn't believe how many I have, and have thrown away.

This is from one file.

 

[achris]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

Yeah, I do the same... Every few months I clean out the folder and start again. :facepalm:... I see one there called 'FixStupid'.... I didn't think you could fix stupid... I thought people born stupid, died stupid....

 

[Bondo]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

Yeah, I do the same... Every few months I clean out the folder and start again. :facepalm:... I see one there called 'FixStupid'.... I didn't think you could fix stupid... I thought people born stupid, died stupid....

Ayuh,.... That's probably ALL the times Don comes in, 'n correct My advice...

 

[ASEAudie]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

After some research, and this forum; It is obvious that this engine was originally equipped with a mechanical fuel pump, someone has rigged their own form of fuel pump.
The customer has been notified of this and he wants it to be right, now I am seeing which way is better and/or more cost effective.
A) Install the correct electric fuel pump with the proper wiring procedure. (Thank you Don for the schematic)
or
B) Install the manual pump and call it good.

Any input on which would be a better choice ?
Thanks,
Audie

 

[Don S]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

I would just install a new mechanical pump. They seem to have less problems than electric pumps. Not so much the pumps fault during failures as the wiring and the switch failing.

 

[Struc]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

Carter does have a Marine universal fuel pump - I'm not sure if it is marked that way anywhere, though. It looks like this:

http://www.jegs.com/p/Carter/Carter-Universal-Marine-Electric-Fuel-Pump/1145238/10002/-1

I bought one with a different brand name (Airtex or something like that), which is just a OEM version when I put an electric fuel pump in my boat.

Just thought I would post that up before you went assuming that the one in there was not a Marine grade pump. As far as I know, they don't make this style pump in a non-marine version, so if it looks like this one, it's probably a marine pump.

 

[ASEAudie]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

Carter does have a Marine universal fuel pump - I'm not sure if it is marked that way anywhere, though. It looks like this:

http://www.jegs.com/p/Carter/Carter-Universal-Marine-Electric-Fuel-Pump/1145238/10002/-1

I bought one with a different brand name (Airtex or something like that), which is just a OEM version when I put an electric fuel pump in my boat.

Just thought I would post that up before you went assuming that the one in there was not a Marine grade pump. As far as I know, they don't make this style pump in a non-marine version, so if it looks like this one, it's probably a marine pump.

It looks identical to that one, so why the rust?

I should probably do just as Don suggests; after all less to go wrong.

 

[Don S]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

It looks identical to that one, so why the rust?

The marine rating means it's electrically safe and will not leak fuel into the bilge. It doesn't mean they are made out of stainless steel so they don't rust.
Usually a few good coats of paint before installing new parts prevents a lot of rust and corrosion. On anything.

 

[Struc]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

It looks identical to that one, so why the rust?

I should probably do just as Don suggests; after all less to go wrong.

Yeah, was just about to reply with what Don Already said.

As far as less things to go wrong... The mechanical pump can/will fail too. It has a diaphram inside that will eventually wear out and leak and/or stop pumping.

I had to put an electrical pump in mine due to replacing my shortblock with one out of a truck, so it didn't have the spot machined for the mechanical pump to bolt up. As Don said before, the electrial pumps are usually reliable - it's wiring issues that usually cause the problems. If they have it wired correctly, with an oil pressure switch, then I'd stick with what you have now.

 

[ASEAudie]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

Ok, so I ordered and received this new mechanical pump; after removing the plate it came to my attention that the push rod that actuates this pump is not there and is NLA. Crap, crap double crap!!!
I printed the typical wiring diagram that Don offered on here, it is nothing like that.
It was installed using scotch locks and the ground wire is connected to itself and the rust may be causing the intermittent problem at the ground wire location.
The starter does not have the Purple/Yellow wire (not even the post to attach it to) nor does the oil pressure switch.

Any ideas on what might be done at this point???

 

[Struc]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

If you want to use that mechanical one, I probably have a push rod laying around from the engines I tore down.

PM me, and we could work something out.

You probably really don't need the starter wire anyway. The engine develops enough oil pressure during cranking to start the pump - I know because my pump stays running for a couple seconds after I stop cranking.

To properly wire the existing pump, you'd probably need to add an oil pressure switch. I bought a Mr.Gasket one, and just used a brass 1/8" NPT "T" fitting from the hardware store to tap off where my oil pressure alarm switch is by the oil filter.

http://www.amazon.com/gp/product/B00068OQ3S

I actually wired up a 30A relay to power my fuel pump, and just triggered the relay with the signal out the back of the oil pressure switch.

 

[ASEAudie]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

I probably have a push rod laying around from the engines I tore down.

If you have the rod that would be great. I believe the original p/n was 17347.
It is for S/N 0D617084 engine, the plate with the cutout already would be awesome as well, the one on it now is solid (I would have to cut the hole)
Thanks, Audie

 

[ASEAudie]

Re: Electronic fuel pump question on 91 Mercruiser 4.3/V6

Well it appears I have wasted my $%#@&*^% time on this POS!!!!!!
Apparently the CAM doesn't have the lobe for the mechanical fuel pump. (The push rod not moving)
Now I'm out a mechanical pump, plus other parts, not to mention my time. Very frustrated