Mechanical fuel pump - multiple bad pumps ??

[MYOUNG]

Be advised... Long fuel pump saga to follow.

I recently bought a 1969 GMC 2500 camper special. It still has the original 350 motor in it. I decided to rebuild the carb because it looked like a filthy mess and while I was at it I also decided to replace the fuel pump and line from the pump to the carb because they were fairly cheap insurance. I went to the local Autozone and picked up a Delphi brand pump and installed it after finishing the carb rebuild. I started the engine and it ran for about 1 minute before suddenly dying. After poking around I realized that the fuel pump was not pumping anymore so I removed it and discovered that the lever arm had failed internally and the tip of the arm snapped off shortly after starting the engine. I returned the pump and got another as a warranty replacement. I installed the second pump and started the engine again. The engine sounded fine and fuel was pumping inside if the inline filter. After about 45 seconds I heard a pop sound from the pump and then the fuel in the filter stopped moving around. 30 seconds later the engine ran out of fuel and died. I removed the second new pump and it had failed the exact same way as the first. The lever arm had the tip snapped off on the inside of the pump. I returned the pump again and then bought a third one from another parts store. The third pump was a Spectra brand it it looked way better. The casting on the pump body was thicker, the mounting boss was thicker, and the lever arm was also thicker steel. The third pump seamed to work as I put about 30 miles on the truck without issue. I was recently setting my ignition timing and adjusting the mixture screws on the carb when I noticed some wetness on the top of the fuel pump. I touched it with my finger and smelled. It was gas. I thought that gas may have been leaking down from the filter and following the fuel line but it was dry. Seconds later fuel began spraying out of the weep hole on the side of the pump and I ran around to shunt the engine off before a fire started. I am beyond frustrated at this point and am about to just put an electric pump on. The old pump that I removed originally looks the same as the rest of the pumps I have installed so I dont know whats going on.

Could vapor lock from extended periods of high idle damage a mechanical pump??

I was running the truck for about 30 minutes while I was moving the timing and mixture screws around. I dont think my fuel line from the tank is plugged as it dumped plenty of gas on me when it was replacing the fuel pump. The inside of the tank looks really good.

Has anyone else had similar issues with quality on these cheap parts house pumps??

[joeydurango]

No offense intended, but you're sure you got the pushrod up on top of the pump's lever arm every time? I don't know if they'll run if you don't - but it can be a bit tricky to get the rod situated properly and I know that can damage the pump.

[MYOUNG]

Joey

No offense taken. I was mindful of making sure i got it on there. I was able to move the pump up and down before I tightened up the bolts to be sure I could feel the push rod contacting the end of the lever arm.

Im just wondering if there is something else that might cause a mechanical pump to fail so soon. Blocked fuel line or vapor lock etc?? I dont know.

Thanks

[Stocker]

Watching this thread..... no idea why they are failing but I can't see how vapor lock or blocked fuel lines could cause the lever arm to break. To be honest I was also thinking some kind of installation error. Any chance of a different length rod? Been a long time since I did one and I don't know if new rods are supplied with the pump, or if you re-use the same rod.

[MYOUNG]

Stocker

I just used the same rod. The new pumps dont come with a new one. The rod itself looks OK. No scratches or wear. Seamed to move up and down very easy. I never removed the rod, just slid it up to place the new pump under it.

I though about trying a carter fuel pump this time but they are even cheaper then the last three I bought. I have seen them for around 15$ when the others are 20$ so im not sure. I have however become quite good at taking the pump on and off at this point.

[dflarsen77]

I just installed a Delphi from autozone but I haven't run it yet. I bought a new dorman brand rod beforehand just in case but the one in there was fine so I just used the old one. This is the first time I've replaced a mechanical pump and man it's so stiff. I had to read around online to make sure it's supposed to as stiff as it is, but I found a few people noting that it only needs to move like .5" and it has a couple hundred horsepower moving it, so I assume it's normal. I even checked out another pump and it was the same. The pump that came out of the truck took maybe 80-90% of the effort. So we'll see. The cheap pumps are only like $18, but I could buy a name brand one if it doesn't work out. We'll see. Let us know how it works out.

[mike16]

it is important to position the push rod correctly/

Back 5-6 years ago there was a rash of bad pumps. they pumped way too much pressure. my first one lasted maybe 7 months befor failing due to tooo much junk in the tank. the next one lasted 3 months but I had to add a fuel filter or two and a holley fuel pressure regulator. each of those pumps cost me about 23 bucks each. life time guarrentee

the next one cost me about 49 bucks and so far it has lasted about 5 years. 1 year guarrentee

so, to answer your question...yes.. its very possible that you can get several bad pumps

watch for too high fuel pressure

[57taskforce]

A little trick to getting the rod seated onto the pump arm correctly is to thread a bolt that is long enough to hold the rod in place away from the arm. Mount the pump up and then remove the bolt holding the rod and it will position it's self. I'll attach a pic of where to thread the bolt. There should alway be a bolt in this hole or you'll have an oil leak. Here you can see the head of the bolt between the radiator hose and harmonic balancer.

[Gromit]

I replaced my mechanical fuel pump on my 1970 C10 with the 350 - in the process, with the old fuel pump off and the end of the line clear I sprayed brake cleaner into the supply line from the tank end and then used my air compressor blower on the steel line from the tank end toward the open end (up by where it attaches to the fuel pump).

Mine did make a popping sound as whatever crap was in my old lines blew out..so I think you are right to suspect the pump is pulling too hard - especially on an old install - easy to rule out though.

There are only a few other possibilities to rule out - one would be the cam lobe that cycles the steel rod that presses the pump arm; (maybe broken or chipped? seems unlikely - usually they wear flat and no longer drive the pump)..

The other is maybe the steel rod has some kind chip in the end or burr or vee worn into it or is the wrong length. I think Summit has several versions of those rods in steel and chromoly and their website will have the spec as to length and diameter.

One other thought - Moly grease on the drive rod ends and pump arm..

[cleanfreak]

I run a jobber store in Ontario , Canada. There is a lot of poor quality mechanical pumps out there right now. Without singling out brands , anything in the lower cost , seems to be poor quality...... Holley or carter make a lower pressure performance pump that is $$$ , but works. Allstar is another company that I have yet to see a major problem from.

Good luck finding a basic replacement...you're gonna need it.

[joeydurango]

I recently (~400 miles ago) put a new AC Delco on my K10. So far, so good, and I think it was about thirty bucks.

[MYOUNG]

Mike16:
Cleanfreak:

Thanks
wow. . I guess I will just buy another one but pay a few bucks more. I just want to be able to trust it. Im not interested in paying some toe truck driver to drag me back to the house. Well thanks for the feedback. Im going to send my 20$ pump back and try a 50$ one. 4th times a charm.

Gromit:

Right after I blow out the line with my air compressor.

[hamjet]

I skimmed over the thread, but do you still have original pump? put it on and see if all is OK. also check the pump numbers and make sure they're not giving you a bb pump.

[BILT4ME]

Most of the aftermarket pumps are manufactured by Airtex, but privately labeled for other makes. I have been recently fighting similar issues on an old Studebaker.

Vapor lock will not "hurt" a mechanical fuel pump. The heat from the vapor lock may degrade the seals prematurely, but that's not the problem here.

The mechanical pumps are designed to suck fuel from the tank. If they cannot get fuel, the diaphragm stays in the vacuum condition and the rod floats between the pump arm and the cam lobe. This MAY be part of your issue, that it impacts an already weak arm when it is pulling hard to draw fuel from the tank.

Your fuel filter should be between the fuel pump and carburetor, NOT between the fuel pump and gas tank. (Pressure side, NOT vacuum side)

You can search the Carter website for a CARTER labelled box unit, but it is still a crapshoot. Otherwise, find an old (30+ years) fuel pump laying in a salvage yard with AC or GM stamped on it, and buy a kit from "Then and Now", rebuild it and enjoy it.

Otherwise, go electric fuel pump as close to the tank as possible, remove the rod, plate the opening, and rig a relay and oil pressure switch and a regulator.

Spectra is doing the same as Airtex, but I have not heard or read any reviews on Spectra pumps.

Airtex is currently going through bankruptcy if that tells you anything........

[Stocker]

Originally Posted by BILT4ME

Your fuel filter should be between the fuel pump and carburetor, NOT between the fuel pump and gas tank. (Pressure side, NOT vacuum side)

Not doubting or questioning you in any way but I'll say what my truck has for whatever that's worth. No issues in the 39 years I have owned it.

Stock Q-jet has the fuel inlet filter. Travel Tanks (twin saddle tanks) were added before I bought the truck, possibly dealer-installed. All three tanks are plumbed to the floor-mounted selector valve, then to the fuel pump. That line, from the valve to the pump, has an inline filter.

I'm posting this info just to point out that whether or not it's technically considered the correct method, it does work.

[BILT4ME]

Hi Stocker!

Yes, it WILL work. As long as the filter is regularly replaced and taken care of. It is harder to suck vacuum that it is to push presure. With the filter between the pump and the tank, it adds vacuum resistance to the line that the pump must overcome to get the fuel. If the filter starts to get dirty, it will not get fuel as well. That SAME filter, clogged to the same level, will last much longer on the pressure side of the pump.

You can only suck so much......... Pun intended.

Again, yes, it CAN work. But if it doesn't already have one, don't put one there.

The mechanical pumps are a diaphragm pump and will not achieve the same suction as what a positive displacement electric fuel pump can generate. In other words, an electric positive displacement pump sucks more than a mechanical diaphragm style pump. It's not as much of an issue on an electric pump.

Originally Posted by Stocker

Not doubting or questioning you in any way but I'll say what my truck has for whatever that's worth. No issues in the 39 years I have owned it.

Stock Q-jet has the fuel inlet filter. Travel Tanks (twin saddle tanks) were added before I bought the truck, possibly dealer-installed. All three tanks are plumbed to the floor-mounted selector valve, then to the fuel pump. That line, from the valve to the pump, has an inline filter.

I'm posting this info just to point out that whether or not it's technically considered the correct method, it does work.

[Stocker]

Originally Posted by BILT4ME

Hi Stocker!

Yes, it WILL work. As long as the filter is regularly replaced and taken care of. It is harder to suck vacuum that it is to push presure. With the filter between the pump and the tank, it adds vacuum resistance to the line that the pump must overcome to get the fuel. If the filter starts to get dirty, it will not get fuel as well. That SAME filter, clogged to the same level, will last much longer on the pressure side of the pump.

You can only suck so much......... Pun intended.

Again, yes, it CAN work. But if it doesn't already have one, don't put one there.

The mechanical pumps are a diaphragm pump and will not achieve the same suction as what a positive displacement electric fuel pump can generate. In other words, an electric positive displacement pump sucks more than a mechanical diaphragm style pump. It's not as much of an issue on an electric pump.

Great additional information, thank you for posting. Makes sense to me!

[snipescastle2]

Might have been said already, but that bolt in the front of the block where you thread a longer bolt to hold the rod,make sure to place a short bolt back in that hole, or you will do one or the other of two things; one, you'll damage the push rod and or break the bolt holding it, or you'll have an oil leak.....just sayin'
Ben

[67ChevyRedneck]

Good info. I've been running a fuel filter under the cab for the past 20 years because of all the horror stories of filter engine fires.

That explains why when I was in my younger days, I added a 2nd filter (one under cab, 2nd between pump and carb) and my truck wouldn't run. Removed one between carb and pump and truck ran again, I guess it was because the pump couldn't handle two filters.

I'm going to redo a lot of stuff when I install my crate motor, maybe I'll plumb in one of the modern GM style metal ones with the screw in fittings between the pump and carb off to the side a bit.

[mike16]

another thing I would recommend, the hole in the passenger side front of the engine block. the one where the bolt screws in to hold the fuel pump rod. I would get hold of a bolt that is long enough to hold that fuel pump rod in place.. and either leave it on the dash or put it up on the intake, so that just in case you need it. It may come in handy on the side of the road. I know this to be true.

[slikside]

Bought a Carter fuel pump off RockAuto a couple years ago, just under $20 IIRC.

Showed up in Pierce box. Same company that makes fire engine trucks. (I had to look that up). Made in USA.

Anyway, that was about 3,000 miles ago. No issues whatsoever.

[Gromit]

Just thought of something else - could it be that the intermediate mounting plate was missing? No offense I hope and you don't sound like the kind of guy who wouldn't notice - but all theories are open until you find out the actual cause.

It does sound like manufacturing issue with the pumps rather than installation though so far.