GM 250 165 L6 Inline engine: New fuel system, failed Airtex fuel pump.

[998cc]

Has anyone else had a problem with new Airtex marine fuel pumps? I installed a new Airtex marine fuel pump about two years ago. It is a marine pump and has worked without a hitch until yesterday. On a local lake, the boat was running strong then suddenly stumbled and quit about a mile away from the boat ramp. I checked everything including the ignition system and the shift cutout circuit and finally determined there was no fuel being delivered to the carb. I luckily had an electric fuel pump stowed in the boat and put it inline. The boat ran great all the way back to the ramp.

This airtex pump had about 10-12 hours use on it over the past two years. The fuel tank, fuel-water filter and all fuel lines, including the filler tube and vent line were all new, USCG approved items and installed at the same time. I am trying to figure out why this thing failed. California gasoline? Sta-bil additive? Just a bad pump?
The pump carried the Airtex brand, not Mercruiser or Sierra. Here is a link to the discussion about this pump in May, 2014.

http://forums.iboats.com/forum/engi...165-250-inline-6-carter-fuel-pump-replacement

Any thoughts are appreciated.

Russ

 

[alldodge]

First I heard of one failing, and even more so soon. Have you had time to check it to see if had anything that may have clogged it. I know every manufacture has lemons, but this is the first of a early failure I've heard of. I would contact AIrtex and see if they can offer anything

 

[998cc]

AllDodge, I haven't taken it down yet. Since everything in the fuel system except the rebuilt carb was new, I didn't expect a foreign body in there. The fuel filter is ahead of the pump as well which should have caught anything from the new fuel tank (tank is cross-linked polyethylene?). I do plan to take the pump apart to see what happened. Good thought on contacting Airtex. Will do after the "autopsy".

Thanks.
Russ
998cc

 

[HT32BSX115]

I am trying to figure out why this thing failed. California gasoline? Sta-bil additive? Just a bad pump?
The pump carried the Airtex brand, not Mercruiser or Sierra. Here is a link to the discussion about this pump in May, 2014.

Howdy,

I replaced the fuel pump on my 97 Mercruiser 7.4L V-8 over 10 years ago using an Airtex pump. I even called Airtex on their tech support line asking them about it. They told me that they are the OEM manufacturer for Mercruiser as well as a huge number of other engine OEM's. SO, if you buy a Mercruiser branded pump, chances are, you're buying an Airtex pump.

Don't know why yours failed ............It's possible that you have a stuck check valve in it from 2 year old fuel (if you didn't drain the fuel before) .........But I wouldn't hesitate to replace it with another Airtex.

And by the way, do not run 2 year old fuel (even if you use Stabil or other snake oil) unless you dilute it with fresh fuel. (3 or 4 to 1)

I always use local gas station regular, E10 fuel, and run (or drain) my fuel tank down to less than 1/4 tank at the end of the season.....and then fill it up at the beginning of the next season. ........ never have used Stabil or other "stuff" either.

Regards,


Rick

by the way,

your favorite freq?

 

[998cc]

Don't know why yours failed ............It's possible that you have a stuck check valve in it from 2 year old fuel (if you didn't drain the fuel before) .........But I wouldn't hesitate to replace it with another Airtex.

And by the way, do not run 2 year old fuel (even if you use Stabil or other snake oil) unless you dilute it with fresh fuel. (3 or 4 to 1)

I always use local gas station regular, E10 fuel, and run (or drain) my fuel tank down to less than 1/4 tank at the end of the season.....and then fill it up at the beginning of the next season. ........ never have used Stabil or other "stuff" either.

Rick. I drain the tank every year and burn the gas in my Toyota Tacoma. The current gas (Arco regular) has been in the tank since November, with added Sta-bil. The gas is now 6 months old, and I plan to use it fairly soon, or again, put it in the Toyota.

Best, Russ

 

[998cc]

No Title

The pump is apart, and the problem is with the suction side check valve?it does not seal properly, and no foreign object was found.

What is very interesting is the way the check valve is installed in the housing. It is a light press fit or possibly an interference fit. (See photos of check valve components.) I couldn't find any fault in the seal, so the stud itself must have slightly backed out of the housing resulting in the sealing washer being raised off its seat.
When I removed the check valve components, they readily popped out of the housing--almost too easily. In my mind, this causes a bit of concern for this method of manufacturing. Also note the machine work on the housing; the casting is not completely machined flat; the raw, un-machined casting Is clearly visible. Perhaps this meets manufacturing tolerances??

 

[HT32BSX115]

Did you test the pump before disassembling it?

 

[998cc]

Did you test the pump before disassembling it?

Rick.
Yes. On the lake, I checked it for fuel flow while trying to determine why the engine died. I saw no reason to set up a bench test for it, and the discovery of the leaking check valve was evidence enough.

Still concerned about the way the check-valves are installed. Studs merely pressed into relatively thin sections of the aluminum pump housing seems a rather bold move on the part of the designer/manufacturers. Could this possibly be a knockoff counterfeit pump?

Russ
998cc

 

[alldodge]

HT does bring up a good point. Had another boat which stopped out of no where and to make a long story really short, turn out the problem was a bad connection. I'm guessing when the boat died you knew the pump was running but no fuel coming out?

 

[998cc]

HT does bring up a good point. Had another boat which stopped out of no where and to make a long story really short, turn out the problem was a bad connection. I'm guessing when the boat died you knew the pump was running but no fuel coming out?

The first place I looked the electrical system; no faults were found. When the boat died Friday morning, I had no clue as to why, so while still on the lake, I tested the various systems, ignition first including the shift interrupt switch circuit. I checked coil connections, verified the distributor mounting was tight. I then opened the distributor looking for points issues or a broken rotor. To test the fuel pump, I simply removed the fuel line from the carb and cranked the engine; no fuel emitted from the open fuel line. I then rigged up an electric fuel pump to get the boat back to the dock/ramp.

I removed the mechanical pump Saturday, disassembled and found no evidence of foreign objects, torn diaphragms, etc. I then bench tested the check valves. The valve on the suction side of the pump allowed air to freely flow both directions while the pressure side valve properly allowed air flow in one direction. The suspect valve very easily came out of the pump housing. There is nothing wrong with the seal itself. I reasoned that the stud had slipped allowing the rubber valve to rise off its seat causing the failure to deliver fuel.

I reinstalled the check valve this morning in the pump body; it works as it should. I just do not trust that it will not become loose in service again.

Russ
998cc

 

[HT32BSX115]

Still concerned about the way the check-valves are installed. Studs merely pressed into relatively thin sections of the aluminum pump housing seems a rather bold move on the part of the designer/manufacturers. Could this possibly be a knockoff counterfeit pump?

Russ
998cc

I would be willing to bet they're all "knock-offs" these days!

Now, having said that, while fuel pumps do absolutely fail, They don't fail very often. Most of the fuel system problems are exclusively stuck anti-siphon check valve, fuel contamination, plugged filters and/or pickup screen, and REALLY old fuel.

I bought my new fuel pump about 10 years ago from Schucks Auto (now O-Reilly's) They actually had an Airtex catalog.

If you decide to stay with an electric pump, be sure that it can supply no more than 6psi or so (or use a regulator) , and install an oil pressure switch so it doesn't run when the engine is not running (key-ON) .

OTOH, if you buy an aftermarket mechanical pump, make sure it has the small hose-bib for the clear hose going up to the carburetor air intake.

Do you boat in Folsom and the other lakes around SAC? (I like Bullards Bar, Oroville and Shasta in particular!!)


Let me also add that after your "repair", if the diaphragm is still in good shape, that pump would probably work for another 20 years!!

 

[998cc]

OTOH, if you buy an aftermarket mechanical pump, make sure it has the small hose-bib for the clear hose going up to the carburetor air intake.

Do you boat in Folsom and the other lakes around SAC? (I like Bullards Bar, Oroville and Shasta in particular!!)


Let me also add that after your "repair", if the diaphragm is still in good shape, that pump would probably work for another 20 years!!

Any replacement pump will be a marine pump.

I boat in Folsom occasionally but more often in the Sacramento River or Lake Amador--nice folks at Lake Amador. Planning a dive trip in Lake Natoma (immediately below Folsom Lake); we'll dive off the boat upstream of the bridge and drift downstream.

The pump: It looks new inside and out. I reinstalled the check valve studs in with 620 green Loctite w/primer. They bench test OK. I toyed with the idea of drilling and tapping the studs axially to take a screw which would hold them in place but decided to just keep the little electric pump in the boat just in case.

Problem solved.

 

[HT32BSX115]

Problem solved.

Simple fix!

73/Rick

 

[998cc]

If anyone is interested, after a few hours running on a local lake, the repaired fuel pump failed again and is now in the parts bin. Being a bit leery of new Airtex fuel pumps, I put the original Mercruiser black fuel pump back in after installing a new diaphragm kit. Runs great......again.

Russ

 

[998cc]

If anyone is interested, after a few hours running on a local lake, the repaired fuel pump failed again and is now in the parts bin. Being a bit leery of new Airtex fuel pumps, I put the original Mercruiser black fuel pump back in after installing a new diaphragm kit. Runs great......again.

Russ

Just found this old post and wanted to update. The old Mercruiser black pump that I rebuilt with a new diaphragm kit in 2016 is still running strong. (Keeping the little electric pump stowed in the boat just in case.)

Regards,
Russ
998cc