I have a thread on another forum, and m1973m's posts there, led me 'here'.Basically, it boils down to this:On Key-on, I bump the starter. With a fuel pressure gauge on the system, the lift pump (prev. owner replaced the lift pump (with what appears to be an Airtex E7153 or replica), as well as added a [crap] Mr. Gasket #12D inline pump (rated at 5-7psi, 35gph) back by the tank. The LP kicks on, and the pressure slowly climbs from zero - ~19psi. Once the LP kicks off, the pressure immediately falls to ~5-6psi. If I sit anw watch it for a few seconds, it'll bleed off to zero PSI.If I repeat, and as soon as it hits 19psi on prime, if I start it, it will fall to zero in about 5-10 secs. I'm wondering if the LP isn't kicking back on after startup. The relay in the fusebox is tripping on, and I've swapped that relay for a known-good one, as well, with no change in results. Is there a way to 'hot-fire' or 'jumper' the LP for testing purposes, to ensure it's pumping when the truck is running? The 'aftermarket' #12D back in the rear of the truck is worthless, IMO. I have a big inline Bosch pump in the garage, but it flows 255LPH and capable of anywhere between 30-90PSI head pressure, depending on the regulator of the system (the pump itself isn't regulated) and I fear that it may be too much pressure for the VP44.I'm not opposed to buying a FASS or AD or whatever, but I'd rather try all other means to ensure that fuel pressure feeding the VP44 is the problem, prior to dropping 4-600$ on another unit.Also, why would some inline pumps state "not for diesel fuel".. Is it the gasket material or something in them that can't handle the fuel's chemical compound?At any rate, let me know your thoughts on the maximum fuel pressure allowed to the inlet of the vp44, as well as ideas to test functionality of the current (new) lift pump in question.Regards,Rick

The ECM provides power to run the lift pump. It was designed to run ONE PUMP. I suspect if the ECM is running both pumps, this may be causing problems. You can make some jumper wires with allegator clips to run directly from the battery to the Airtex pump and check its pressure. I think I would remove the Mr. Gasket pump. Sounds like someone did some hookey wiring job to cut corners. Anything other than a stock or stock type replacement pump that draws the same or very similar amperage should be run directly off the batteries with a relay. The ECM can handle a stock OEM type lift pump but not a larger performance pump. Running a larger pump off of the ECM is asking for the dissaster of burning out the ECM pump power supply in my opinion. I have an Airtex e7153 pump relocated to the frame below the fuel tank and pushing through a 1/2" Big Line Kit through the OEM filter housing all the way up to the IP with 1/2" line. Just bumping the starter, static pressure was about 20 psi new, once I start the engine the fuel pressure drops to about 17-18 psi idling. Max WOT load pressure drops down to about 8-10 psi. Not perfect but works well for the wife on a stock truck. If your truck is not stock, get the Air Dog or FASS. The Mr. Gasket pump is a gas fuel pump. The seals and pump output may not be compatible with diesel fuel nor the output of the pump adequate to provide the fuel volume a diesel requires under a load.

Thanks. yeah, it's 100% stock truck. The Mr. gasket Green pump (what he added) is for diesel, and it's wired separately (not in conjunction with the Airtex.) sorry, I didn't point that out in the original post.I'll try to make some jumpers and such, an test the fuel pressure with the Airtex running straight from battery (and not from ECM) this afternoon. I'll report my findings.

I am still relatively new to the diesel scene but I wonder if you could use that 30-90 psi bosch and just put a regulator between it and the VP44. Seems like that would be cheaper to do than buying a fass or ad and would still get the job dun. I have seen regulators on ebay for like less than 50 bucks and if you allready have a good pump I would think that would be the best of both worlds. Maybe not even notice any drop in psi under wot... Boy I hope I didnt just make my self look like a total noob.

I am still relatively new to the diesel scene but I wonder if you could use that 30-90 psi bosch and just put a regulator between it and the VP44. Seems like that would be cheaper to do than buying a fass or ad and would still get the job dun. I have seen regulators on ebay for like less than 50 bucks and if you allready have a good pump I would think that would be the best of both worlds. Maybe not even notice any drop in psi under wot... Boy I hope I didnt just make my self look like a total noob.

The only issue I see with that, is that pressure builds heat. Heat kills the VP44. If it were 30psi with regulator, might not be too bad, but even that sounds like it would build a lot of heat, 90 would definitely get the fuel cooking.

Could you regulate it to around 18 psi after bosch and before vp... Not sure how all this works so I am learning as I go, not trying to hijack his thread but just curious?

I may have missed it, but how are the two pumps wired? I know you said differently, but what is controlling the power?And just to be clear, your getting fuel pressure until you start it, then none?

The Airtex uses the OE wiring. The green POS pump in the rear is wired relay-hot with a toggle switch.Yes, as for fuel pressure, I turn the key to RUN, bump the starter, and the Airtex engages, raising pressure to ~19psi. It runs for about 15 secs or so, then when it shuts off, (engine still off) the pressure immediately falls to ~3-5psi. Once I start the engine, it falls to zero.offroad, your thought process is the same as mine, right now. And I, too, am somewhat of a diesel newb.

The Airtex uses the OE wiring. The green POS pump in the rear is wired relay-hot with a toggle switch.

Yes, as for fuel pressure, I turn the key to RUN, bump the starter, and the Airtex engages, raising pressure to ~19psi. It runs for about 15 secs or so, then when it shuts off, (engine still off) the pressure immediately falls to ~3-5psi. Once I start the engine, it falls to zero.

The first half sounds normal, with nothing running there should be no fuel pressure.

What if you just start the truck without the bump?

---------- Post added at 03:24 PM ---------- Previous post was at 03:23 PM ----------

Could you regulate it to around 18 psi after bosch and before vp... Not sure how all this works so I am learning as I go, not trying to hijack his thread but just curious?

I wonder what the extra flow would do to heat the fuel in the tank thou?

The Airtex uses the OE wiring. The green POS pump in the rear is wired relay-hot with a toggle switch. Yes, as for fuel pressure, I turn the key to RUN, bump the starter, and the Airtex engages, raising pressure to ~19psi. It runs for about 15 secs or so, then when it shuts off, (engine still off) the pressure immediately falls to ~3-5psi. Once I start the engine, it falls to zero. offroad, your thought process is the same as mine, right now. And I, too, am somewhat of a diesel newb.

Perhaps I missed where you mentioned it but have you tried replacing the fuel filter?

The first half sounds normal, with nothing running there should be no fuel pressure.

What if you just start the truck without the bump?

---------- Post added at 03:24 PM ---------- Previous post was at 03:23 PM ----------

I wonder what the extra flow would do to heat the fuel in the tank thou?

Good point on the heat. Not really sure, or even how much heat will be produced.

Perhaps I missed where you mentioned it but have you tried replacing the fuel filter?

I have the filter, just havent replaced it yet. Gonna try that as soon as it stops sprinkling...

---------- Post added at 06:51 PM ---------- Previous post was at 05:53 PM ----------

Ok, so I ran a few tests.

First, I tried the key-on, engine-off pressure test again, both with/without the little pusher pump..

~20psi, then slowly drops to zero about 10 seconds after LP shuts off..

I replaced the FF and did it again.. This time, it went up to almost 30psi, then settled down to zero after about 20 seconds..

Even engine running, same result..

So I disconnected the LP from the harness and made a power/ground jumper from the battery, straight to the LP.

Refired the engine, and had the LP running directly off of the battery. It went from 28psi, slowly down to ~8, paused for a second or two, then rapidly went on down to zero. This is with the pusher pump on, and the LP directly connected to the battery.

It started to rain a little, so I had to end my troubleshooting. I want to 'test-fit' the Bosch inline pump in place of the LP with a direct connect to the battery (not using the ECM's LP circuitry) and see what that results in. If it works, yay! I'll monitor the heck out of the FP and 'beta test' that setup for a couple days. If not, then I'll look into dropping the coin on an Airdog or FASS, or the likes..

If the Bosch does sustain for a few days, with no issues, then I'll feel much better about spending the money on a better lift pump.

I'm really leaning (at this point) of it being a LP issue, though.

Thoughts?

Comes down a simple solution... You demand volume is higher than supply volume... 1. Your tank pickup is plugged or restricted. 2. Lift pump(s) are not making the grade.

2a. Lift pump(s) being in series might be restrcitive. 2b. Overflow valve failed and stuck open.

Comes down a simple solution... You demand volume is higher than supply volume...

1. Your tank pickup is plugged or restricted.

2. Lift pump(s) are not making the grade.

2a. Lift pump(s) being in series might be restrcitive.

2b. Overflow valve failed and stuck open.

Thanks!

I'll be dropping the tank tomorrow (provided it doesn't rain again, but is desperately needed), as he mounted the pusher pump on the inside rail, beside the tank. Don't think he thought that one through ;).. So I'll pop the tank open and check the sock filter while it's down..

Come to think of it, one of my past rock crawlers, a jeep cherokee 4.0L had a stumble/hesitation issue, and it came down to the sock filter in the tank had a single "clean" spot, about the size of a pencil eraser. The rest was completely clogged.. I replaced it, and the Jeep ran fine after that..

Here's what the Jeep's sock filter looked like LOL

The only clean spot on it:

The Jeep it was in:

i agree to the sock clog in the tank, we did a friends truck recently where he had to stay over 1/2 tank or the truck would stall and if he hammered on it the fuel pressure would drop to nothing and the truck would stall he would leave truck off for a few min. then fire and go again (this is with a full fass system) so i dropped tank and found the pre-screen was clogged to the bowl that houses the pick-up and the sock itself was clogged. i could not get a new pick-up assembly from dodge because it was superseeded with the fuel pump assembly retrofit this was dodges answer to cummins sorry lift pumps so we tore out the pre-screens and replaced the sock. spun on some new fass filters and reinstalled tank that truck ran great after these repairs. i might also note that he delivered fuel for a living so the fuel in his truck was often unfiltered but the cost was great:thumbup2:

i agree to the sock clog in the tank, we did a friends truck recently where he had to stay over 1/2 tank or the truck would stall and if he hammered on it the fuel pressure would drop to nothing and the truck would stall he would leave truck off for a few min. then fire and go again (this is with a full fass system) so i dropped tank and found the pre-screen was clogged to the bowl that houses the pick-up and the sock itself was clogged. i could not get a new pick-up assembly from dodge because it was superseeded with the fuel pump assembly retrofit this was dodges answer to cummins sorry lift pumps so we tore out the pre-screens and replaced the sock. spun on some new fass filters and reinstalled tank that truck ran great after these repairs. i might also note that he delivered fuel for a living so the fuel in his truck was often unfiltered but the cost was great:thumbup2:

Awesome, thank you. I'll definitely check this out tomorrow, weather permitting.

Hopefully its a simple sock cleaning and it'll be up and running again.

Hopefully its a simple sock cleaning and it'll be up and running again.

Amen to that!

(btw, I'm prior service, 67Y, 19K)

---------- Post added at 07:35 PM ---------- Previous post was at 09:51 AM ----------

Ok, so today, I decided to drop the tank, and check out the sock filter.. What a freakin clusterfudge!

Apparently, someone with little clue, much imagination, and no money decided to fix something. I'll post pics once I host them (can't upload to the forum yet.)

let's see if I can explain it..

They took the feed and return lines from the sender assembly, then siliconed those connections closed (on the assembly.)

They then drilled and tapped two 3/8" barbed fittings through the tank's top. One was a 'new' return, and the other was a 'new' feed. Inside the tank, they installed a 'feed' hose from the one barb, down to the bottom of the tank, and installed a small filter. You know, the ones that are about 3/4" diameter, metal, a nipple on one end (inlet) and threaded fitting on the other. And yes, they put it in backwards. Not to mention, a total PITA for servicing.

I took the filter off, as I saw some junk in it. I started taping it out onto a paper towel, and you would not believe the crap that came out of it. (picture coming)

So, I went to Advance, and dug through the filters until I found one with 3/8" nipples on each end, as well as a couple feet of fuel line, and some fuel injection clamps. $36.87 total, including a Gatorade and some beef jerky LOL

For the reinstall, I left the hose inside, lay on the bottom.

Moved the pusher pump from inside the framerail (where it was buried behind the tank) to the outside of the framerail. I added the new inline filter to between the tank and pusher pump, then plumbed it all back together, and reinstalled the tank.

Turned the pusher pump on, turned the key on, bumped the starter, and watched the pressure go to 27-28psi. Started the truck, and the pressure stayed around 24-28psi.. YAY!

Drove it around the block and it stayed above 15, even with a few hard pulls through the gears.

I got back home, and left it run for about 5-8 minutes, and the pressure stayed steady at 22-25psi. With it still running, I turned off the pusher pump, and the pressure slowly dropped to about 3psi. Turned it back on, and it came right back up.

I think my 'new' Airtex is crap, and won't pull enough fuel, or the pusher pump is too much restriction when off. I can test that tomorrow, by removing it from the loop, since it's now outside the rail, and accessible.

I can say, though, that this is a dog, compaired to my '96 p-pumped, #10 plated truck LOL Nowhere near as responsive, either.

Afterward, my neighbor across the street (he's got a 98.5 24V 5speed) was talking to me about the truck, and I mentioned that my lift pump is possibly dead. So he says "I have a new in-tank assembly with pump and all the parts for the retrofit, including the manifold piece that goes in place of the lift pump. It's in the garage somewhere. If you want it, you can have it, as I've no need for it now."

I'm like "Sure."

So anyhoo, I'm gonna tag the truck tomorrow, and drive it to work on Friday (6 mi. round trip) and see how it acts. Only thing I have concern with now, is the lethargic acceleration. But again, that could be due to driving the p-pump truck with it's super-responsiveness and tons-o-power

glad you got your toy on the road and concider the low power a base line, sttart hot rodding the new truck and you will realize the advantage of newer technology

glad you got your toy on the road and concider the low power a base line, sttart hot rodding the new truck and you will realize the advantage of newer technology

Thanks, Koyote.

I'm kinda excited that I didn't (yet) have to buy an injector pump, as initially thought when I bought the truck a couple weeks ago.

I don't want to turn the wick WAY up, but I'd definitely like some more 'GO' in it. My 5 y.o. daughter wants me to "put a smoke pipe on it like your blue one". IOW, she wants me to stack it. I might, but I'll definitely keep it a tad quieter than the blue one. It's 4" turbo-back, no cat, no muffler, to a 5" step, to 7" stack. It's friggin' loud.

The power steering in the new one is really stiff, like it's low on fluid. I assume it's got a leak, as there's a PS fluid bottle in the cupholder. I'll be doing Mike's vent reroute this weekend, too, eliminating the bottle by the radiator.

Then, will be a lift pump replacement of some sort. After that, I'll look into power adders.

---------- Post added 08-05-2010 at 09:02 AM ---------- Previous post was 08-04-2010 at 08:37 PM ----------

Pictures:

I would of washed out the fuel tank seeing that crude... Ewww!

THat's the wierd part. I examined the tank really well inside, and there was no trash in it.. It musta sucked it all up already LOL