Fuel pump help

[Burning Oil]

Sock will come off. Did you ever blow out the lines? While tank is down it would be a good to blow them out. Use a clean catch bucket so you can see what comes out. I did mine one time and was shocked at the amount of crap that came out.
If you remove tank sock You can keep your A/C pump and add a 30 micron prefilter to it. I make the special fittings for it just let me know if interested.

[DmaxMaverick]

Try the same thing with the fuel cap loose (or removed). You have more than just a flow problem. Still, it's not the sock, or you wouldn't have had the trip you did. It's plugged, or it's not. In all likelihood, the tank is not venting, and the system is suffering under vacuum once it's ran a while.

[racer55]

Try the same thing with the fuel cap loose (or removed). You have more than just a flow problem. Still, it's not the sock, or you wouldn't have had the trip you did. It's plugged, or it's not. In all likelihood, the tank is not venting, and the system is suffering under vacuum once it's ran a while.

I second this.

[arveetek]

I didn't make it home last night. I made it within 2 miles of the house. I had 0 psi on the fuel pressure gauge, and trying to prime the system resulted in no movement of the needle at all. While I was there I removed the fuel cap, but no change.

I came back 30 minutes later to tow it home. Pushed it in the garage, tried priming it again and instantly had 9 psi. Started right up, and held a constant 5 psi while running for about 10 minutes or so before I called it a night and went to bed.

I've tried leaving the cap loose or off before while troubleshooting, and haven't noticed a change.

Whenever the problem occurs, I get zero fuel flow. Let it sit a while, and she's back to normal.

Casey

[Kennedy]

FYI radiator shops generally also do gas tank repair. I'd suggest getting fuel level as low as you can and drop the tank then inspect and have it cleaned/flushed to be certain it's not a bio fouling situation. Otherwise you might end up back inside again.

[ginger743]

Have you checked the voltage at the pump while it's failing ? Seems you've checked everything else. Put a volt meter across the leads going to the pump when it's on and your pressure is zero. You may have a serious voltage drop at the pump.

Jerry

[Robyn]

The problem is most likely in one or more of the Rubber hoses.

Cut them all off the system, install a ferrul fitting on the steel line then remove the fitting. Use the ferrul as a retaining "Bump" install all new hose and clamp with stainless clamps.

The issue can be on the suction side or the pressure side.

The Transfer pump in the IP can suck really well and if there is a blockage it will pull a vacuum and suck the filter dry very fast.

What happens is that the hose core delaminates from the reinforcing layer and then can suck flat and choke off the flow.

On the pressure side a "flap" of inner hose liner can flip into the flow and stop up the line, the resultant restriction allows the transfer pump to pull a high vacuum on the line and suck the filter dry.


REPLACE the rubber, all of it, on both the feed and the return lines.

Blow out the steel for good measure too.

This should correct the problem for good.

As mentioned before, Mickey mouse a 5 gallon fuel jug and sit it in the passenger floor area and run a hose to a lift pump and rig it out the window and under the hood as a test.

I personally would just replace the Rubber and be done with it.

Good luck

Missy

[racer55]

Have you checked the voltage at the pump while it's failing ? Seems you've checked everything else. Put a volt meter across the leads going to the pump when it's on and your pressure is zero. You may have a serious voltage drop at the pump.

Jerry

*2
I am wondering if the location you are drawing power from is expanding from high current draw and loosing contact.

[arveetek]

Thanks for the suggestions everyone.

I have checked voltage at the pump several times, but I have not been able to check it when the symptoms appear. I'm usually on the side of the road when it quits for good!

All rubber lines from the lift pump forward are brand new. I installed a new Racor filter, and ran my own rubber line from the lift pump up to the filter, and ran a new line from the filter to the IP. The only stock rubber line left is between the hard steel line on the frame rail and the fuel tank.

I haven't had any biodiesel in the tank in over 4 months. I'm still going to drop the tank and see what's in there once again.

Casey

[ginger743]

Hi Casey,

It wouldn't be too difficult to run an alternate power source to the pump , heck you could even use a cigarette lighter plug for the power source. The only " problem " would be to open the leads to the pump which you would have to splice back together after you finish the test.

Wouldn't take very long to do the tests.

You could also add extension leads to your voltmeter so you could monitor the voltage as you drive and catch it when it fails.

Jerry

[Robyn]

Replace that last piece of rubber line while your at it.

The issue is obviously a failure to deliver fuel.

If you have replaced all the stuff from the Lift pump forward then the issue is either the rubber line that connects the tank or the pickup tube somehow.

I have seen many rigs that have a failed lift pump run just fine until a filter change, then it gets noticed as the filter will not refill.

This has definately gotten to be interesting for sure.

Missy

[arveetek]

If you have replaced all the stuff from the Lift pump forward then the issue is either the rubber line that connects the tank or the pickup tube somehow.

This has definately gotten to be interesting for sure.

Missy

I don't think 'interesting' is the right word here!

Yep, everything from lift pump forward is new, including the injection pump!!! I'm pretty sure I ruined the original IP with this whole fuel starvation fiasco. I'm sure it was old and weak anyway, but still....

Casey

[arveetek]

It was the stupid 'sock' in the tank.

It passed the visual inspection twice before. Last night I dropped the tank again, and this time I took the sock off and tried to suck some air through...and it wouldn't hardly pass any air through!!

The 'sock' was new less than 20K miles ago. But, it's a different design than the OEM sock. I took the old OEM sock off my old pickup assy, and it had no restriction whatsoever. The OEM sock also has a bypass valve built in, that will allow fuel to come in through the end if the sock gets restricted.

The old sock is nearly round with nothing inside. The new sock is flat with a plastic mesh inside, so it's actually several layers. Even after cleaning it, it still didn't flow much air.


(New sock on left, OEM sock on right)





I put the old OEM sock back on the newer pickup assembly. I also blew the lines out from the lift pump back. Got a little bit of junk out, not much. I also replaced the rubber line from the tank to the hard line.

With the last Airtex pump and before these changes, the best pressure I had before starting was 7 psi, dropping to 4psi while idling, with the pressure falling to zero after running a short while.







With the new AC Delco pump and the repairs made last night, I have 10.5 psi before starting, dropping to 6 psi while idling, with no further pressure drop after running.






I actually made it to work with no problem! I still had 6 psi while idling after driving 22 miles.

After all this time, it was that stupid sock.......

I do think that the aftermarket socks are probably not the best product to be putting in our diesel fuel tanks. It could be that our homebrew bio fuel may have clogged this sock as well.

Thanks for all the advice everyone. Sorry I didn't follow all of it as soon as I should have.

Casey

[Burning Oil]

Said it atleast 6 times to relocate the sock to the trash can.
Then you went and stuck the sock back in there!!?
Keep an eye on it as you will probaly be droping the tank again.
Could have saved the cost of the IP as Im sure it was fine.

[arveetek]

Still running great! Been driving all weekend without a single drop in fuel pressure.

I even had time to change the tranny fluid yesterday, which was long overdue. I did the flush out method: took the tranny cooler return line loose and pumped the old fluid out into a clear container. Worked really well. That old fluid was looking nasty...fortunately it didn't smell burnt.

I'm so glad to have my favorite vehicle running right once again.

Casey

[Burning Oil]

Thats great, hope it runs well for along time.
How much fluid did you go through? I did that once and used like 16 qts before it ran clear.

[arveetek]

Thats great, hope it runs well for along time.
How much fluid did you go through? I did that once and used like 16 qts before it ran clear.

I show that the 4L80E holds 14 quarts on a full fluid change. Yes, I ended up using a full 4 gallons when it was all said and done.

That tranny holds a lot of fluid!

Casey

[SickSpeedMonte]

Wow, I have had almost the exact same experience as you...

When I got my '93, the underside was rusty. I had to replace the brake lines, trans cooler lines, and the fuel lines. While replacing the fuel lines, I noticed that the lines on top of the tank were shot, so I replaced the sender with an aftermarket one from Quanta Products.

I replaced the fuel filter as well. At first, all was well. I even towed my C230 about 75 miles to get it fixed at a dealer. A few weeks later, it started starving for fuel. The bowl would not fill just like yours. I think the air gets in there when you crack open the bleeder by the way; there is a vacuum in there otherwise, which is why the IP doesn't like it and the truck doesn't run.

So I replaced the LP, seemed easy enough to do and the Airtex wasn't too expensive from Advance Auto. Still had the problem.

I couldn't hear the LP running with the truck running (too much other noise) and I couldn't get fuel to the bowl unless I jumped the LP, so I figured the OPS took a dump. I got a Delco OPS and did the relay mod while I was in there. Bled the system, and still had the problem when the truck warmed up. It happened when I was low on fuel, so I put 5gal in it and the truck ran home fine. So at this point, I'm thinking that either the tank is creating a vacuum, or the pickup isn't picking up. The next time it happened, I cracked the cap and it didn't help... so out comes the tank again.

The sock was brand new (<100 miles, clean as a whistle), so I verified that the pickup depth was right, and it was. I pulled a vacuum on the pickup, and it held. I verified that there were not clogs in the lines and no kinks in the soft portions, put it back together, and still had the problem a few days later. It was only happening when the truck warmed up, consistently. So I swapped the Airtex LP out under warranty, and I still have the problem.

So then I started talking to a parts supplier tech guy (don't want to name names...) and he told me to get a gauge on the supply line. I get one and install it just before the filter to see if the LP is pumping right. I also pulled the filter out thinking maybe there is a clog in there somewhere. I blew air in the supply line of the fuel manager, which blew the little spring for the heater out. Put it back together and nothing changed. The gauge showed 4psi at idle and less than 1 when I revved it, and then it cut off.

Then he instructed me to replace the fuel manager because there is no way I blew air in there without blowing up seals. So I figure if I have to replace it, I'd might as well take it apart and see what happened, maybe fix it with new seals. The thing was perfectly fine, no blown seals. But now I have managed to render my heater unuseable while trying to disassemble it. The insulation on the wires was all gummy and now there are exposed wires. The fuel heater is so much money that it's only like $10 more to get the whole fuel manager, so it looks like I'll be spending ~$200 on that...

I was also told that if the regulator/check valve on the return line of the IP is suspect, to just replace it. I took that off and blew some air at it (never actually touched the nozzle to the check valve to try to create a seal or anything). Still somehow, I think I might have trashed that. There is a black O-ring in there that looks like it rolled out of its seat.

Now that I have read your thread, I'm pretty sure that I have been chasing my tail this whole time and it was that damn sock. I don't have the stocker anymore, but I did a little experiment last night. I disconnected the fuel line going into the LP and blew shop air towards the tank, trying to blow the sock off. I don't know if it worked or not. I put it all back together, got plenty of fuel to the fuel bowl, but it wont start. I think that little check valve is indeed comprimised.

So from here, I need to replace that check valve, get a fuel heater one way or another, and see if it still stalls under load. Regardless of what happens, I think I still need to drop the tank and get an OE sock on there. I don't know if I should stick it out with the Airtex LP or try to return it towards a Delco...

[racer55]

Wow, I have had almost the exact same experience as you...

When I got my '93, the underside was rusty. I had to replace the brake lines, trans cooler lines, and the fuel lines. While replacing the fuel lines, I noticed that the lines on top of the tank were shot, so I replaced the sender with an aftermarket one from Quanta Products.

I replaced the fuel filter as well. At first, all was well. I even towed my C230 about 75 miles to get it fixed at a dealer. A few weeks later, it started starving for fuel. The bowl would not fill just like yours. I think the air gets in there when you crack open the bleeder by the way; there is a vacuum in there otherwise, which is why the IP doesn't like it and the truck doesn't run.

So I replaced the LP, seemed easy enough to do and the Airtex wasn't too expensive from Advance Auto. Still had the problem.

I couldn't hear the LP running with the truck running (too much other noise) and I couldn't get fuel to the bowl unless I jumped the LP, so I figured the OPS took a dump. I got a Delco OPS and did the relay mod while I was in there. Bled the system, and still had the problem when the truck warmed up. It happened when I was low on fuel, so I put 5gal in it and the truck ran home fine. So at this point, I'm thinking that either the tank is creating a vacuum, or the pickup isn't picking up. The next time it happened, I cracked the cap and it didn't help... so out comes the tank again.

The sock was brand new (<100 miles, clean as a whistle), so I verified that the pickup depth was right, and it was. I pulled a vacuum on the pickup, and it held. I verified that there were not clogs in the lines and no kinks in the soft portions, put it back together, and still had the problem a few days later. It was only happening when the truck warmed up, consistently. So I swapped the Airtex LP out under warranty, and I still have the problem.

So then I started talking to a parts supplier tech guy (don't want to name names...) and he told me to get a gauge on the supply line. I get one and install it just before the filter to see if the LP is pumping right. I also pulled the filter out thinking maybe there is a clog in there somewhere. I blew air in the supply line of the fuel manager, which blew the little spring for the heater out. Put it back together and nothing changed. The gauge showed 4psi at idle and less than 1 when I revved it, and then it cut off.

Then he instructed me to replace the fuel manager because there is no way I blew air in there without blowing up seals. So I figure if I have to replace it, I'd might as well take it apart and see what happened, maybe fix it with new seals. The thing was perfectly fine, no blown seals. But now I have managed to render my heater unuseable while trying to disassemble it. The insulation on the wires was all gummy and now there are exposed wires. The fuel heater is so much money that it's only like $10 more to get the whole fuel manager, so it looks like I'll be spending ~$200 on that...

I was also told that if the regulator/check valve on the return line of the IP is suspect, to just replace it. I took that off and blew some air at it (never actually touched the nozzle to the check valve to try to create a seal or anything). Still somehow, I think I might have trashed that. There is a black O-ring in there that looks like it rolled out of its seat.

Now that I have read your thread, I'm pretty sure that I have been chasing my tail this whole time and it was that damn sock. I don't have the stocker anymore, but I did a little experiment last night. I disconnected the fuel line going into the LP and blew shop air towards the tank, trying to blow the sock off. I don't know if it worked or not. I put it all back together, got plenty of fuel to the fuel bowl, but it wont start. I think that little check valve is indeed comprimised.

So from here, I need to replace that check valve, get a fuel heater one way or another, and see if it still stalls under load. Regardless of what happens, I think I still need to drop the tank and get an OE sock on there. I don't know if I should stick it out with the Airtex LP or try to return it towards a Delco...

Take the sock completely out and put an inline fuel filter/screen in pre LP-much easier to change when it gets dirty when on the frame rail.

[DmaxMaverick]

Take the sock completely out and put an inline fuel filter/screen in pre LP-much easier to change when it gets dirty when on the frame rail.

To repeat what I've said before.....

In my educated opinion, this is not good advice. Add a lift pump pre-filter if you wish, but do not remove the sock as a course of corrective or preventive action. If your sock is plugging, or giving you ANY grief, you have a SERIOUS fuel quality problem. The sock is nothing more than a relatively coarse screen, which will catch metal flakes, pebbles, sand, algae or other large debris that may plug the pickup tube inlet. If your sock is plugging up, you would have had to replace dozens of filters by this time. If the sock is plugged, the tank and entire fuel system needs to be cleaned and flushed. It's that simple. I hear the sock getting blamed as a "problem", while it almost never can be. Of course it can fail, but it will never cause the problems it is blamed for. It will almost always be the result of a problem, and almost never be the cause of one.