Using the lift pump prime?

[TooManyIdeas]

Hi I am new to the world of Nissan diesels and Diesels in general. I recently purchased a 1982 Datsun 720 with a SD22. For some reason it lost it's prime. I think after reading your articles extensively it was dry rotted fuel lines. I replaced those and am currently trying in vain to bleed the system. Everyone says to pump it until the (foamy) fuel is purged.

About how long does this process take and is there a faster way to get it done. Any info would be greatly appreciated

[philip]

Everyone says to pump it until the (foamy) fuel is purged.

Did you read all of *Fuel Filters*??

This particular post deals with priming the pump correctly: PRIMING

It is up to you to diagnose sufficient availability FROM the fuel tank, THRU the filters. When these sources flow fuel adequately, then it is possible for the check valves in the primer pump to be faulty. Another member just detailed such an experience.

[asavage]

Everyone says to pump it until the (foamy) fuel is purged. The old owner simply said to pump it a "Crap Load".

Open the IP's bleed screws, unscrew the priming pump knob, operate plunger until fuel without air bubbles comes out the IP bleed screws, close screws, stow the priming plunger, clean up.

About how long does this process take and is there a faster way to get it done.

Under a minute of pumping the plunger. A little longer, when you include finding the 10mm box-end wrench, opening the IP bleed screws, and afterward spraying cleaner on the IP and hosing it all down.

However, if you're pulling air from some cracked line somewhere, you may never achieve the "no bubbles from bleed screws" state, in which case you're going to have to do some further work to find out why. And if either filter is plugged, it can be very difficult to get significant flow out the bleed screws. If you don't know when the secondary filter was changed, I strongly suggest replacing it first, and then bleed it. I know it's not cheap, but it's cheap insurance. Bacteria can grow in the filter if there was water separated out in it, and bacteria will clog a filter, even if it doesn't have many miles on it. That's another reason why you want to drain the filter regularly, and esp. before storing the vehicle.

[TooManyIdeas]

I got it. It was a bad fuel filter. I don't know if it was cracked or if the previous owner had put the gasoline type on, but I ordered one from Nissan and slapped it on. Priming took less than 30 seconds which was amazingly quick compared to before, and now she runs like a champ.

[asavage]

I got it. It was a bad fuel filter I don't know if it was cracked or if the previous owner had put the gasoline type on, but I ordered one from Nissan and slapped that puppy on.

This was the primary fuel filter you replaced, that fixed the problem?

[TooManyIdeas]

I guess there was a crack in it because I would spend almost 30 minutes priming the pump and would not purge the air out. I even loosened the line on the injectors and cranked it. That worked for about a minute, then it died out again. Finally the filter that I ordered from Nissan came in. I noticed it dodn't look like the one on my truck so I swapped it out and priming took no time at all.

[philip]

Got a question for you, my buddy and myself are at a loss on what's going on with the SD-22. We pulled the injectors and took them over and had them rebuilt (engine was running before I pulled the injectors). We've put them back in, connected everything except the connection of the acutal line to the injector, and turned the enigne over to get fuel to the injector, but nothing comes out even after repeated prining of the IP (which I'm not sure is necessary), What are we missing? When we pump the primer with the vent bolts slightly loose, we get fuel out and hear recirc in the tank, any help appreciated.

Bill

Bill: The Primer Pump will move volume but little pressure. So far, yours is working fine.

But to reach the fuel injectors, fuel has to be pushed past each of the four injection pump plungers and their respective Delivery Valves (which is a strongly spring loaded one-way check valve). The injector line also has to be vented at the injectors. The Primer Pump won't do that.

[TooManyIdeas]

Ok, so the new fuel strainer fixed the problem or so I thought. It ran great for about 2 weeks and started getting worse and worse fuel mileage. I figured it was because I was going 70 plus on the highway but then it started struggling more and more at startup until finally it won’t start at all. Now the engine doesn’t have air in the system and the priming pump requires noticeably more effort to push (good thing?). Also with the bleeders opened and pumping fuel shoots out like a squirt gun. After I closed the bleeders and push the primer down to lock it, fuel squirts out from underneath the pump handle (I assume that’s bad)and when pumped I noticed what I can only describe as “whistling” coming from around the OFV, is that normal. In my novice and inexperienced opinion I’m think maybe too much pressure?
If I'm right what is the fix, if I'm wrong how the hell do I fix it?

[philip]

SNIP- Also with the bleeders opened and pumping fuel shoots out like a squirt gun. After I closed the bleeders and push the primer down to lock it, fuel squirts out from underneath the pump handle (I assume that’s bad)and when pumped I noticed what I can only describe as “whistling” coming from around the OFV, is that normal? -SNIP

Typical and correctable is considerable leakage from around the primer pump shaft as the pump is operated. Replace part. Lift Pump

With the injection pump bleeders closed, operation of the primer pump will overcome the OverFlowValve pop-off pressure. That threshold pressure (about 18 psi) is the "wheeze-bzzzt" sound you hear each time you pressurize it. Normal.

However, you said AFTER you close the bleeders -and- depress/screw down the primer into the "stowed" position that fuel is squirting out. Are you meaning dripping for a while until dry or continuing to drip while the engine is running? The latter is NOT normal ... of course not. See above link.

[asavage]

What Philip said. The OEM primer leaks when you're using it. Unfortunately, that's normal. Replacing it with the newer style will fix that, but you don't need to replace the primer if it leaks when you use it.

If it leaks when it's in the down/locked position, you have to replace it.

[TooManyIdeas]

However, you said AFTER you close the bleeders -and- depress/screw down the primer into the "stowed" position that fuel is squirting out. Are you meaning dripping for a while until dry or continuing to drip while the engine is running?

No it would squirt out as I was pushing it down. As for leaking while running, I don't knoww cause it doesn't run. It's cool that you guys eliminated the primer from the problem, but what is the problem then? Maybe one of the injectors is bad, this is my first time with a diesel so I moght have not realised it was misfiring. My engine vibrates alot on idle (I thought that was normal for a diesel)

[asavage]

It ran great for about 2 weeks and started getting worse and worse fuel mileage. I figured it was because I was going 70 plus on the highway but then it started struggling more and more at startup until finally it won’t start at all.

Poor fuel mileage . . . a fuel leak, wrong fuel, failed compression, dragging brakes. Hmmmm. You didn't mention if power had dropped off, just that starting is difficult. If you have power loss too, I always look for fuel feed problems, usually air via a cracked line or plugging filters (crap in fuel or algae/bacteria).

Now the engine doesn’t have air in the system and the priming pump requires noticeably more effort to push (good thing?).

Back to suspecting the secondary fuel filter. Would explain hard starting, but not decreased fuel mileage.

Also with the bleeders opened and pumping fuel shoots out like a squirt gun.

Scratch the secondary fuel filter then . . . the primer sucks fuel from the primary filter and feeds the secondary filter, thence to the IP, so good fuel flow at the IP's bleeder screws means good flow through the filter.

After I closed the bleeders and push the primer down to lock it, fuel squirts out from underneath the pump handle

Leaks are normal, "squirts" is probably too bad to use. I'm guessing.

If I'm right what is the fix, if I'm wrong how the hell do I fix it?

Bear in mind that your starter is not going to put up with all the excess cranking forever, and you don't even want to know what one of those cost.

Does the cranking speed seem "regular", or does it speed up and slow down?

I can't get both your hard starting, fuel flow from bleeders, and poor fuel mileage in the same cause (unless you have bad fuel). Sounds like multiple issues, one masking the other. You need to drop back to basic troubleshooting. Test compression and write down the values as a baseline for future comparison, retest every glow plug (when removed, not a current-only test), make certain that the IPC motor is running when you begin cranking, drain water from the secondary fuel filter (if you have an '82 or newer filter/base assy.), drain water from the fuel tank (small, 12mm bolt at the bottom of the tank), test for suspect fuel (gasoline mixed in with the diesel, for example, will give all of those symptoms, but for very long). WVO in your fuel will also do it, giving rough idle, poor starting, poor mileage, but you'll also likely get lots of smoke too.

I'm just throwing a bunch of things at you, because there are too many symptoms to account for any one thing, except bad fuel. Are you trying some fuel "experiment"?

Did you try to "blow out" the secondary fuel filter with compressed air (a big no-no)? If so, you may have blown a hole in it, and let crap ruin the IP -- which it will, and not slowy either.

I hope something above sounds good to you, because I don't know where to go with this unless you can do a compression test, test the GP system, and verify the secondary filter and fuel composition.

[TooManyIdeas]

Ok after getting pissed to the point of using colorful 4 letter adjectives I claimed defeat and found a competent Diesel Mechanic. Turns out that the wire that powers the glow plugs is wired directly to the battery, oh and it broke off. DURRR. Obviously the truck won't start if the glow plugs aren't getting power. Stupid me I look at the glow plug light go off and on and figure it would you know WORK. So now the truck is working again, however I'm still getting what I believe is crappy fuel mileage (somewhere between 20-25 MPG) And I've been noticing an occasional drop in power (pedal to the floor and slowing down ). Any ideas?

[philip]

Ok after getting pissed to the point of using colorful 4 letter adjectives I claimed defeat and found a competent Diesel Mechanic. Turns out that the wire that powers the glow plugs is wired directly to the battery, oh and it broke off. DURRR. Obviously the truck won't start if the glow plugs aren't getting power. Stupid me I look at the glow plug light go off and on and figure it would you know WORK.

Ok then ... it is HIGH time you read and understood How the AutoAfterGlow system works and get your mind around how the system operates. The glow plugs are NOT wired directly to the battery.

So now the truck is working again, however I'm still getting what I believe is crappy fuel mileage (somewhere between 20-25 MPG) And I've been noticing an occasional drop in power (pedal to the floor and slowing down ). Any ideas?

Well ... you're the "TooManyIdeas"man. Let's do some deductive reasoning based on your knowledge base. Hehehehhe

An "occasional drop in power (pedal to the floor and slowing)" will occur by not downshifting. Believe it! Keep that gearbox stirred up. Were I to source the complaint to the mechanical arena, diesels simply slow down as fuel delivery is cut back. No surging, no backfiring ... just slow down as if you backed off the throttle. Fuel delivery restrictions.

Fuel mileage is a VERY subjective matter and worthy of a new discussion thread.

[TooManyIdeas]

If the glow plugs are not wired to the battery from the factory then the old owner did some "Creative" wiring. Which is not surprising since I notice a strand of brown EXTENSION CORD going from the battery to the cab (probably the stereo). Of course the battery isn't even the one that is supposed to be in the truck and is held in with a bungee cord. Don't suppose any of you gents got pix of what the factory setup is supposed to look like

p.s. Id send pix of this redneck engineering but i haven't a clue on how to attach photos