Priming the fuel system

[oldmax82]

Hello:

I was changing my fuel filter yesterday and now can't get my 82 wagon running. Specifically, I disconnected the drain and sensor wire from the old filter and allowed it to drain. After installing the new filter I pumped the top of the filter housing as it says to do in the book. Probably pumped 500+ times and never really felt like I was pumping fluid and did not get bubbles or fuel out of the vent opening like is says in the book. It started and ran for 5 or 10 seconds before dying. Tried to start it again but it was a no go. I pulled off the filter and manually filled it with diesel fuel ( there was not much fuel in the new filter) and tried again without any results. I'm sure I have run the system out of fuel and went on to try to purge air by pulling off the low pressure rubber hose next to the #1 injector which looks to be the beginning of the return flow system. Using my hand vacuum pump I attempted to prime the system. It holds 26 inches of vacuum so no fuel is being drawn through the system from that spot. Al Savage has posted some pictures of the return from the IP so I will see if I can find the right line and attach my vacuum pump. Is it common for the pump on top of the fuel filter housing to be non-functional? If anyone has suggestions please chime in.

Thanks, Terry

[asavage]

After installing the new filter I pumped the top of the filter housing as it says to do in the book. Probably pumped 500+ times and never really felt like I was pumping fluid and did not get bubbles or fuel out of the vent opening like is says in the book.

If this was routine maintenance (ie there was no problem beforehand), I'll guess that the priming pump isn't working. You should definitely get fuel out the vent within, oh, 50 pumps.

. . . went on to try to purge air by pulling off the low pressure rubber hose next to the #1 injector which looks to be the beginning of the return flow system. Using my hand vacuum pump I attempted to prime the system. It holds 26 inches of vacuum so no fuel is being drawn through the system from that spot.

I don't think that you can purge the IP via that line. It's a spill-over line from the injectors, not the IP. You need to use the line from the IP housing's return line, not the line from the injectors return.

Al Savage has posted some pictures of the return from the IP . . .

The one in this post?

. . . so I will see if I can find the right line and attach my vacuum pump. Is it common for the pump on top of the fuel filter housing to be non-functional?

I think that someone recently found a bad priming pump on their Maxima, so I suppose that they go bad. You might get one from MidnightZ in Woodinville, unless he wants to keep it.

[oldmax82]

Thanks for the tip. Using your pictures of the return fuel line and my mitivac hand pump I primed the IP. The car started on the third attempt and seems to be running fine now.

I appreciate the help. I don't think I will be changing the fuel filter on this car again without first filling up the filter with diesel. Chalk this one up to youth and inexperience (at least with diesels).

Terry

[davehoos]

I ve often had to use air pressure in the tank to bleed system.

there are a few vehicles on the farm here that the primer pump needs to be bled before they will pump.father inlaws gemini[mark 1] and our pajero the non return valves has disintergrated.

the isuzu has a loop of hose that easy to get at.normally i use a rag and air blower at the filler cap.undo a bleed screw and dont use too much air pressure.a piece of heater hose a rag and blow into the tank will be enough.

also ive parked the vehicle on a hill with full tank of fuel and let syphon through if its a quick filter change.or as the bleed screws often frozen in possition turn the filter upside down and bleed it through the drain tap.

[asavage]

Thanks for the tip. Using your pictures of the return fuel line and my mitivac hand pump I primed the IP. The car started on the third attempt and seems to be running fine now.

That's good news.

I don't think I will be changing the fuel filter on this car again without first filling up the filter with diesel.

If you're still making your own fuel, it's probably a good idea to carry around a spare filter, and if need be you should be able to change it by the side of the road. In that event, a working OEM priming pump is a good idea. See if you can scrounge one up. Don't listen to Matt, he just likes his electric pumps a bit too much

[goglio704]

Don't listen to Matt, he just likes his electric pumps a bit too much

I didn't even mention an electric pump in this thread. I have only used an electric pump on a Maxima twice. Don't knock it till you've tried it. I only used it temporarily to get the engine started anyway. It is a holdover from my Olds diesel days (it was permanent in that case). BTW, I have at least one dead primer pump myself.

[asavage]

Oh, I've tried electric fuel pumps. The aftermarket ones, especially, are some of the most unreliable hardware on the planet. If you rely on one, it'll leave you stranded somewhere, eventually.

[goglio704]

I had a Facet that was problematic on the Olds after it had run 40 or 50k. Later I used a Lucas for about 20k. It was removed before the rest of the car was scrapped and still starts unprimed Nissans today. I'll agree that it was propably the least reliable part of the fuel system, but it made chores like draining water, purging air, and changing fuel filters very easy. Like a lot of things, it is a tradeoff. I don't have one permanently installed on a Maxima. I would be concerned about throwing off the required internal pressures. Cummins did use a mechanical lift pump to feed the VE pumps in the Gen 1 Dodges, but they may have had an internal difference to allow for that.

[asavage]

Cummins did use a mechanical lift pump to feed the VE pumps in the Gen 1 Dodges, but they may have had an internal difference to allow for that.

You'll note that when people began using homebrew fuels in those early Cummins, the lift pumps would fail and the low feed pressure would take out the expensive IP.

[goglio704]

I knew that was an issue with the 2nd generation Cummins trucks. My employer had it happen with #2D on a 1999 model. Mucho $$. I don't know the particulars of that fuel system, but it isn't a VE pump. It doesn't surprise me that it could happen on the VE systems too. The Lucas pump that I have doesn't produce significant restriction when it is turned off. Less than 2" Hg. I don't know about a failure scenario though. A check valve plumbed in parallel with an electric pump would provide restriction protection separate from the pump. Centrifugal pumps are inherently minimal in their restriction when turned off, but their use as a lift pump is rare since they are poor about self priming.

[asavage]

I think you're right, in that it wasn't the VE IPs that had the lift pump failures affect the IP, I think it was the later VP44. There is at least one (and probably more) kit for the Dodge/Cummins truck that measures fuel pressure between the lift pump and the IP, due to the expense when the fuel pressure falls off out of the lift pump (for whatever reason).

[oldmax82]

Thanks for the tips and commentary on purging the system of air. I do keep an extra fuel filter in the car so I will need to buy another one soon. My guess is if I filled the filter with fuel before screwing it in that it would start up and run OK. I'll give that a try the next change. At least I know where to attach my vac pump so I suppose I need to carry it in the car as well. I am still making my own fuel and use B80 in the winter and B100 the rest of the time. Recently, my son has been using the maxima as his daily driver and it has about 20k miles on biodiesel. So far so good, although this car smokes more than I like even with biodiesel. Since I now have a TDI and F250 I may have to let the maxima go when my son gets his own rig.

Thanks, Terry

[atalamark]

Well the rain stopped long enough for me to take the flashlight outside and check things over.

The hand primer doesn't appear to work. I loosened the vent screw and pumped and pumped. Nothing, a few small bubbles but on fuel.

So it appears I need to buy a vacuum pump. Any suggestions for a cheap functional one?

After reading Terry's post I was unclear as to weather or not he attached the vacuum pump to the line after the filter, to get air through the filter, and then primed the IP out line or if he just hooked up the pump straight to the IP out line..........does that make sense?

Mark E Kaylor

[asavage]

If your priming pump doesn't work, use the Mity-Vac or equivalent on the IP's return line. Keep pulling until no bubbles appear. It will take a while. I do not think that pressurizing the tank will do the job, and you can very easily deform a fuel tank, with only 3-5 PSI, so my advice is to use the vac. pump.

There is rumored to be a repair kit for the priming pumps. I have to look into it for the same pump on a Toyota diesel PU I'm working on. If I find out more about it, I'll post. Meanwhile, you only need the priming pump when you change the filter, so it's not really a big deal.

[glenlloyd]

... I have to look into it for the same pump on a Toyota diesel PU I'm working on.

What Toyota diesel PU are you working on?

steve a