Rebuild or Replace a 283 R15 Fuel Pump Model # 4926?

[rslingerland]

Gentlemen:
I am rebuilding a 1962 CC 283 R15 V8 (Engine Serial # 823,662), and have now come to the problem of the fuel pump. On the flange the part # is 4926. After scouring all of the fuel-pump related correspondence on this board, I don't see that model listed. I have attached pictures below for you.

My question is: do I rebuild or replace? I don't know that it DOESN'T work, butyour discussions concerning ruptured diaphrams, gas in the oil, etc. makes me gun shy. Does anyone have experience with the insides of this model? One diaphram or two? Repair parts available? Or, do I replace, and if so, what are your suggestions? I've followed the heated discussion here about electric vs mechanical fuel pumps, but am no closer to a decision.
Thanks very much in advance for any help you can offer,
RSlingerland

[mfine]

My opinion is that the old mechanical fuel pumps are less reliable and less safe. As such, I prefer a low pressure (not for fuel injection) electric pump and an oil pressure cutoff safety switch.

Modern fuel, with or without ethanol, evaporates faster and can make it hard to start after a boat sits for a few days. Your starter needs to crank the entire engine to slowly run the fuel pump until the carb is full enough for the engine to start. The electric pumps fill the carb much faster and save starter wear. They are also ethanol resistant and will not leak fuel into the engine oil even if they do fail.

The oil pressure cutoff switch will send power to the fuel pump for a few seconds while the starter is engaged and then only when it senses oil pressure. This prevents the fuel pump from continuing to run after the engine stalls and may also save your engine from an oil problem.

[quitchabitchin]

These pumps are easily rebuildable and/or fairly cheap to have rebuilt if you send them to the right people. I have done both, but found that if you are using pump gas, the boiling point of ethanol enhanced fuel is much lower than full strength gas and I was experiencing a vapor lock issue that the mechanical pump could not overcome. I recently made the switch to an electric pump with the oil pressure switch. I haven't had more than a few minutes of run time, but in the event that the fuel does start to boil, the electric pump will push the vapor through instead of compressing it.

Mechanical pumps are completely okay as well and work on most applications, including some pretty high horsepower builds. I chose electrical mainly to combat the vapor lock issue I was experiencing. Then and Now Automotive in Massachussetts can rebuild that pump for a reasonable price as long as the housing is not cracked.

[charlesquimby]

For a double diaphragm mechanical marine service pump check NAPA M73021. CQ

[George Emmanuel]

Your fuel pump doesn't have a primer lever, but for those who do have such, physically priming the engine before starting saves a lot of angst. I had a Gray 620 in my Cavalier, and at 6volts would take forever to prime. Using the primer made a huge difference.

Avoid ethanol if possible!

George

[joanroy]

Interesting discussion. I'd like to learn more about mechanical vs. electric fuel pumps and potential problems with ethanol fuel. I'm running 1992 Marine Power 350s with mechanical pumps and electronic ignition in my 36 and had stalling problems last season. Both engines start and run fine and will cruise at speed without a problem. When we throttle back to slow down to come into harbor, one or sometime both engines die. Of course coming into port is the worst time to loose power. All fuel and electrical componenents have been replaced and thoroughly checked out. In other words, there's nothing wrong with anything that could cause this stalling problem. When an engine conks out and after waiting for 5 or 10 minutes it will start right up and run fine again. Have any of you guys had a problem like this due to issues with ethanol fuel? Fuel pressures been checked out and is correct. Is it a vapor locking or fuel boil problem caused by ethanol? Unfortunately non-ethanol fuel is not available in my location.

[rslingerland]

Thanks to all of you who responded. Although my predilection is always to go with the old, I will now look into electric fuel pumps with oil pressure shut-off.
RSlingerland

[mfine]

It is not just ethanol that boils off. Even modern ethanol free gas is more volatile than it was in the past.

The cutoff and pump are two seperate items. The cutoff is small and can be feed on where the small oil port is for the oil pressure gauge. For the pump, you are looking for one that is regulated at 4-6 psi, give or take.

[Greg Wallace]

"winter blend" gasoline that finds its way to warmer climates can be an issue as well. The difference in vapor pressures results in vapor locking in warm temps and engine spaces.

[joanroy]

Will electric fuel pumps totally eliminate the possibility of vapor lock problems, and if so, what brand marinized electric pump is recommended?

[drrot]

"Coast Guard Approved" is the big thing to look for.

[dag55]

Carter P4389 is the electrical pump to go, for a marine small block V8.

[joanroy]

Thanks Dag, l found the Carter pump on line for 81 bucks. If my stalling problem continues this coming boating season, I'll switch to electric. I'm going to drain my tanks and start with fresh fuel to see if that makes a difference. Gotta give the mechanical pumps one more try.

[mfine]

I believe the switches I used were Holley 12-810 (about $30 each) and I second the Carter p4389.

[mfine]

Will electric fuel pumps totally eliminate the possibility of vapor lock problems, and if so, what brand marinized electric pump is recommended?

I won't say totally, but if you mount the pump away from the engine and heat, closer to the fuel tank, it should help a lot. You still need to make sure the fuel line from the pump to the carb is not getting over heated especially if it is a copper line. If you replace copper, or add a new pump make sure you maintain a ground connection for the fuel tank.

[joanroy]

Mfine, thank you for for the info and recommending the Holly oil pressure shut off switch. If I decide to go electric, having another level of safety added on to protect my engines is reassuring. Sounds like a winning combination.

[evansjw44]

Just maybe your problem isn't with the fuel pump. You say stalling occurs as you pull back to idle after running at speed. If you were having fuel starvation it would show up at speed, usually. I'd suggest you consider this. I don't know which carb you have (Holley or Carter/Edelbrock) but both have automatic chokes with a "fast" idle set up. If the carb/choke is not set up properly the your idle speed may be set with the fast idle cam in place to raise the idle speed for cold or cool operation then droping out of place for hot operation. With the engine hot the fast idle cam should drop away so that the idle adjustment is set on normal stop. If your normal idle is set with the fast idle cam lifted the when you pull the throttle back to idle the idle speed is too low and the engine will stall, but re-start easily once the throttle is opened slightly.

Another possibility is carbuerator icing. When you pull back the throttle after running at speed ice can form in the throttle plate ares and choke off the fuel. Again, cracking the throttle will allow the engine to restart easily. There should be some exhaust cross-over to warm the base of the carb. On the V8s some use a heat isolating spacer between the carb and the manifold to prevent percolation and some do not. Look for condensation around the base of the carb after running.

Last, you could be starving for fuel at idle and maybe not at speed. The reason would be wear on the fuel pump lob of the cam shaft. GM cam shafts in the 1960s were notoriously soft. If the fuel pump lob is worn then the stroke of the fuel pump is shorter than designed thus at idle the fuel flow is low and the carb starves out. If this is going on the engine will be hard to re-start.

Another thought is to look for an air leak in the fuel line. A leak in the fuel tank dip tube or near the top of the tank will make it harder for the fuel pump to deliver fuel, especially at low speeds. Typically this shows up when the fuel tank is less than half full.

My last thought is the throttle linkage if you have the Carter Carb. There are two places in the linkage set up that can affect the idle setting. One it on the carb. There is the expected idle setting on the carb base. But with the 60s Morse control and cable linkage, there is a stop on the throttle arm under the cover that sets the cable travel length. This stop needs to be set such that when the throttle lever is pulled all the way back to idle, the cable does not pull the throttle plate below the carb idle stop. Its a curious arrangement but on the Carter carb, there is a spring that allows the throttle plate shaft to be rotated beyond the idle setting choking off the fuel flow leading to stalling at idle. I can give you a procedure to properly set this up if this might be your issue.

[mfine]

To be clear, my comments on the electric pump solving issues only relates to solving the fuel evaporating out of the carb issue, and help reducing vapor lock (if not mounted on near heat and the fuel line is protected).

If those are not the causes of your problem, I can't promise a new pump will do anything to help.

[evansjw44]

I definitely have the problem of dry float bowls after sitting for 4 days. I just crank till I have fuel and then my engines start right up. The extra cranking is tough on the starter I suppose but it lubs up the engine before it starts which is not all bad. I recently read an article that said Carter cars, maybe Edlebrock too, have plugs in the bottom of the float bowl that leak slightly and are the reason the float bowls go dry. I don't know if I believe that.

[charlesquimby]

Carter WCFBs And AFBs Cannot be beat. Probably the two best carbs for marine V8s. Never had much luck with the Edlebrocks, so I no longer use them. CQ

[joanroy]

Jim, thank you for your trouble shooting tips. I'll check out all the possible solutions to my stalling problem before I switch off my pumps. The reason I think it may be related to a vapor locking problem is due to the fact that the engine won't restart until it's allowed to sit for ten minutes or so. Both engines do the same thing, but thankfully at different times so I'm able to maintain control with the running engine while I wait a while to restart the stalled engine. Seems to me it' has to do with a heat problem either with the fuel or the carb and by waiting to restart something cools off. Engines run at160 degrees and this problem is intermittent and has only been happening for the last couple of seasons. Frustrating!

Carbs are rebuilt Rochester Quads

[mfine]

I definitely have the problem of dry float bowls after sitting for 4 days. I just crank till I have fuel and then my engines start right up. The extra cranking is tough on the starter I suppose but it lubs up the engine before it starts which is not all bad. I recently read an article that said Carter cars, maybe Edlebrock too, have plugs in the bottom of the float bowl that leak slightly and are the reason the float bowls go dry. I don't know if I believe that.

We had the exact same behavior (bowl going dry) with the Rochester Quadra crap on the Penn Yan, a 2 barrel Holley on my CC when I first got it, and on an Edelbrock Carter clone, so if it is a leak issue, it is incredibly consistent.

On the PY, we needed to keep the fuel tank above half or it would need to crank forever before starting if it started at all. It also had a major vapor lock issue where after you shut down for 20 minutes, you had to wait hours for it to cool before it would restart. Super annoying! Multiple mechanics couldn't fix that for 30 years, but finally going to an electric fuel pump allows it to start right up after sitting for 20 minutes or 6 months, even when the tank is run way down.

[mfine]

Jim, thank you for your trouble shooting tips. I'll check out all the possible solutions to my stalling problem before I switch off my pumps. The reason I think it may be related to a vapor locking problem is due to the fact that the engine won't restart until it's allowed to sit for ten minutes or so. Both engines do the same thing, but thankfully at different times so I'm able to maintain control with the running engine while I wait a while to restart the stalled engine. Seems to me it' has to do with a heat problem either with the fuel or the carb and by waiting to restart something cools off. Engines run at160 degrees and this problem is intermittent and has only been happening for the last couple of seasons. Frustrating!

Carbs are rebuilt Rochester Quads

I am very sorry to hear you have two Quadrajets!

I am not so sure your issue is vapor lock. Almost sounds more like carb ice. The vapor lock on our PY was the opposite. If you shut down or stalled, it would start right back up. If you let it sit for a bit (10-20 minutes?) and the heat had time to boil off the fuel that was not flowing anymore, then it would vapor lock and not start for hours until it cooled off. Not a lot of cooling happens in just 10 minutes. Carb ice would behave like you describe. It would stall the engine, and then not allow a restart until the engine heat had a few minutes to melt it.

[joanroy]

Mfine, I take it your not crazy about Rochester Quads. Prior to rebuild I looked into switching them out for Hollys, but I had a clearance problem. Only a couple of inches or so between the flame arrestors and the hatches. 350s are stuffed where Chrysler Crowns once resided.
Anyway, I'm interested to learn more about Icing. I actually saw it for the first time on the old Hercules W I'm messing with. After running for a while the base of the manifold where the Zenith attaches was covered with frost. Didn't seem to be a problem on the W but I can see how it could cause problems with the 350s. If their icing would it be visible on the outside of the Rochesters or manifold like it is on the W?

[quitchabitchin]

If you switch to electric, pay attention to the type of pump you use. I purchased an Airtek pump and it is required to be mounted within 12" of the engine and after the fuel filter. Some electric pumps, such as the Holley in-line pumps, are pusher pumps and should be mounted near the fuel tank. Shielding the fuel lines from heat will also help to keep vapor lock at bay.

On the subject of Carburetors, I am a big fan of Carters. With the evolution of the Carter to Federal Mogul and eventually to Edelbrock, a lot of quality was lost with each generation. While the newer Edelbrocks work well for many, I would rather rebuild the old Carter's than make the switch. Good, rebuildable cores are readily available and are inexpensive to have rebuilt.

[evansjw44]

I had a memory dump today and re-discovered an article I read that might be pertinent. It was in Hemmings Motor News within the last two months as I recall. The article described a similar idle stalling problem. The article said the Rochester Q-jets have two float bowls, one for idle and one for high speed jets. The author had his Q-jet carb rebuilt but the builder did not set the idle float height incorrectly. Resetting fixed the problem. Consider that most V8 marine engines have the carb sitting at an angle off level we might have a clue.

But then, I could have this mixed up. Thought I'd share.

[Tom Gruenauer]

I found this http://www.how-to-build-hotrods.com/ele ... -pump.html
My brother hooked his up with the wrong sender, the pump would not turn on when cranking.
A "tee" in the line for oil pressure sender and the correct marine fuel pump.
Tom

[joanroy]

I didn't know my Rochesters had two float bowls. I've never taken one apart and had them rebuilt five or six years ago. When my throttle back stalling problem started two years ago I had messed with my engine alignment that year. Never really got the alignment right the first time and had to lower the back of the engines down quite a bit. Engines stall when throttled back and of course reducing speed brings the bow down. I wonder if the combination of increasing engine alignment pitch and bow drop is messing up the idle floats. Never had a problem before I changed alignment. If I take the top off a carb, how do I figure out if the floats are set properly?

[quitchabitchin]

You will need the correct setting measurements for you particular carb. You have a "Drop" setting which is the distance from the float to the top plate when the floats are dropped all the way as in a fully empty bowl, which would equal a fully open needle & seat. The other measurement is 180 degrees of this with the top of the carb upside down and the float all the way up, or a fully closed needle. You should be able to find these settings online or they would be included in a rebuild kit.

[dag55]

Q-jets don't have double floats. Carter/Edelbrocks do. Have you disassembled and cleaned your carbs? Do that before do anything else!
Have the motors been running ok earlier? You mentioned that the carbs where rebuilt a couple of years ago? I think it is a lot of speculation going on here...