Fuel pump... was thinking

[yARIC008]

So I've got most of the parts to do the electric fuel pump install, but I got to thinking. The mechanical pump on the truck is, from what I know, the original pump, and still works just fine. Only problem with it is when you have a fuel leak you have to crank the engine to prime the system. Has anyone ever thought of having the electric pump in parallel with the mechanical one? Basically have a tee upstream and downstream of the two pumps, have one way valves down stream of the two pumps, and then only run the electric one when needed, such as when priming the system or if the mechanical pump fails.

Sound like a good idea or is that just stupid?

 

[icanfixall]

Thats always been a great idea. Its just the plumbing issues involved in doing it. Non return valves are the park that killes this modification. Diesel fuel will find the smallest leak in any valve system. Diesel will find the leak that water or gasolene can't. If diesel can't find a leak you don't have a leak.

 

[Agnem]

One of the benefits to an electric pump installation is you eliminate 1 of 2 ways contamination of the crankcase oil with fuel can occur. Leaving the mechanical pump in will delete that feature. Also more plumbing means more opportunities for air intrustion, and greater difficulty in troubleshooting. I just don't see the benefits outweighing the negatives. I'd rather see you just leave the mechanical in and not put on the electric.

 

[jim x 3]

Eric: I'd agree with Mel here - keep it simple.

Et al: beyond that, my past experience, limited that it is, doesn't square with the general forum view that fuel leaks/air intrusion is a big issue. I have a complete stock fuel system in my '88 (except for pickups in the tanks). Maybe I've just been lucky, but I don't have any issue with the stock arrangement. When I change out a fuel filter (with the truck nose up on a sloped driveway) I fill the replacement filter 3/4 full. I crank less than 10 seconds to restart and though there is some stumbling, the engine never dies. I never crack or purge anything. OTOH, I have driven my truck home 150 miles with a non-functional electrical system. I couldn't shut it off enroute, the dash gauges were haywire, and I had no lights (it was daytime), but I got home. This would not have been possible with an electric fuel pump.

Regards,

 

[Jbevs]

I have had that exact idea, though without one way valves. I thought it was a good one because you have the electric pump to purge to system if need be or use incase the lift pump fails, yet you still have the mech. lift pump so that the truck can run entirely under it's own power in the event of electrical problems. I had pondered installing shutoff valves before and after both pumps to isolate one or the other if I wanted. However, all this is just an idea and I'm sure others (mel, icanfixall, etc) know better than I on this issue.

 

[bike-maker]

I'm currently working on one of these setups. Midnight Rider was the one that sparked my interest in it. I've got a carter electric pump, a ball valve for the supply to the mechanical pump (in case it takes a dump and starts filling the crankcase with diesel), and diesel rated check valves for each of the supply lines - 1 before the mechanical pump, and 1 right after the electric pump. I will run the pump off of a relay, and only use it when glowing the plugs before start up, or when priming the system.
I did take into consideration the additional possible fuel leaks, but I think having 2 seperate fuel pumps, and being able to run the engine off of either one, is worth it.
I'll try to post a picture of the pump with the ball valve / check valves on it when I get home tonight.

 

[jim x 3]

Guys, keep it simple. Though I'm running the mechanical pump, I'd prefer the electric pump only over a setup with both pumps, Tees, ball and check valves, and the mess of piping and connections required. The day you install all this stuff, its clear how it works. Three years from now when something goes *****, will you remember how it all works? Will your documented notes and service info be sufficient to allow you to troubleshoot? IMHO.

Regards,

 

[TWeatherford]

I say go for it. Maybe I'll be the first. Since I run vegetable oil I'm always tearing my system open and having to crank to prime. Its not difficult, really, especially after the amount of practice I have. I refuse to run an electric only, because they fail way more often than a mechanical pump. I do not desire to ever change out a pump on the side of the road, and replacing the mechanical pump every 100,000 miles for good measure will prevent that need. Also, no electric pump except the $1000 + ones are proven to pump assorted fuels (WVO, WMO, ATF etc) reliably for many miles. Plus the above mentioned, electric fuel pumps require electricity.

My idea involves two manual three way valves. When I desire the electric pump, I flip two valves. When I desire manual again, flip them back. You have 3 fittings, and less than two feet of additional hose. I don't see the complexity in that, nor much added room for air leaks if its done with a little common sense. Would have to remind myself to use the electric pump maybe once a month or so to keep it from going bad from just sitting so long, as I'd only use it to prime, troubleshoot, and in the rare event of a mechanical fuel pump going bad on me.

 

[Jbevs]

That's another point I forgot to mention, and another reason I like to keep the mechanical lift pump. I think it will do better than most electric pumps at moving heavier fuels reliably.

 

[flareside_thun]

I strongly believe in the practice of KISS. However, what's wrong with putting an electric FP on a bypass line? What I'm saying is, why not have the best of both? The reliability of the stock manual lift pump, but also the electric whenever you need it? I'll draw it up on paper and scan it in to show the setup I'm talking about.

 

[bike-maker]

Man, didn't realize this was going to turn into a debate.
Myself, I would greatly prefer to have an electric pump, but I wouldn't trust it not to leave me stranded after a healthy dose of old motor oil. For my situation, I think running both mechanical and electric pumps in parallel is the best solution.
So here's the setup I have so far. Seems pretty straight forward to me. The only real concern I have is the additional fuel line running from the electric pump up to the filter housing. We use all of these components in the generators at my work, and rarely, if ever, experience any fuel leaks. All of the fuel leaks I have tracked down in my truck have turned out to be biodegraded O-rings.
After all the concern about diagnosing leaks, I think I'll add another ball valve right before the electric pump so I can run the truck off of either pump at one time to diagnose any fuel system issues.

 

[GOOSE]

Mike, your system looks simple and easy. I do believe having a backup system out weighs any negatives involved. I once spit out a rear U-joint on a truck of mine. I rolled to the red light, put the driveshaft in the bed, locked the front hubs and pulled off as the light turned green. Some will say the 4x4 system just adds maintenance and more to go wrong, it saved me from a wrecker and being late to work that day. A spare lift pump system, electrical and mechanical, can do the same. Good luck on the install and please keep us posted, pics included.

 

[yARIC008]

Seems like there is a split right down the middle, 50% like the idea, 50% don't. Personally I think I'm one that does like it :O I like redundancy.

I think as long as you do a decent job on the install and avoid leaks there isn't much of a problem with it. Isolation valves around the mechanical pump could cut it off if it started leaking into the crankcase.

I have a complex filtering system/heater bypass on my cooling system and even 7 years later was able to figure it out again when a leak sprung up. I've since corrected the problem and shouldn't get leaks anymore.

Anyways, whatever floats your boat... or in this case, whatever fuels your injection pump...