OK, well, in further futile pursuit of a resolution to my problem (https://www.ford-trucks.com/forums/1...and-decel.html ), I installed a new Walbro fuel pump yesterday. It did rasie my idle fuel pressure, from 58 to 62 psi. I would assume, but didn't check, that my running/WOT pressure is also a little higher now as well. Unfortunately, it didn't solve my bucking/knocking problem.

I now also see a ton of air in my Racor pre-pump filter. I had a small amount of air in there previously, but I had finally gotten it out. Now, with the new pump, its a crazy amount. The top third of the filter bowl is aerated foam.

I realize I introduced air when I replaced the pump, but I closed the shutoff valves on both sides of the Racor first, as well as clamping off the fuel line about an inch before the pump inlet. So, changing the pump should not have done anything to introduce air into the Racor.

The aerated fuel appears to be coming into the filter inlet, but there is no way that air is being introduced between the tank and the Racor. I have a bottom feed sump, and ALL connections have been sealed, both with teflon pipe sealant on the threads inside, as well as the outside being completely encased in black RTV. I did not disturb any of this when I installed the new pump.
I did drain and open the fuel bowl ( the factory one on the engine), to check the filter. It looked nice and clean, so I just put it back in. I also reused the existing o-ring. There is no fuel leak. Is it possible that the re-used o-ring could be allowing air into the fuel bowl, but not be leaking fuel? I wouldn't think so, given the high pressure. If air could get in, then 60+psi fuel should be getting out.

Ideas?

 

1. Are you sure that the clear fuel filter housing is sealed tight into the filter head, or does not have a crack anywhere in it? Either would allow air to get sucked in.

2a. Did you drop your sump down? If so, it might no have resealed properly, but if that were the case, you'd be leaking fuel there.

2b. What size fuel line did you run between your sump and Racor filter?


For either 2a or b above, if there is too much restriction in your fuel suction into the Racor filter, then your new pump would have created a higher level of suction between the filter and the pump, and this would cause an increase in differential pressure across the filter element itself which could very easily cause a release of dissolved air and create foam inside the filter on the low pressure side (pump side of the element). This could also be caused if you are using too "tight" of a filtration media in the Racor pre-pump filter.

 

1.) It is as tight as I am comfortable making a plastic bowl, in fear of causing it to crack. I had gotten the air out, with the old pump. I did NOT loosen/empty,etc... the Racor in any way shape or form, when installing the new pump.

2a.) No. I did not touch the sump at all. It is not leaking. As I said, ALL connections are thoroughly encased in black RTV.

2b.) I have 3/8 fuel line from the sump to the inlet of the Racor PS120, and 5/16 line from the outlet to the fuel pump inlet. Fuel pump outlet to motor is factory stock lines. The 3/8 from the tank is an upgrade from stock. The 5/16 to the pump is the factory size. FFD/Ryan made it clear that the Walbro pump should be a drop in stock replacement, albeit with a higher volume capability. There was no mention of any need for larger fuel lines.

The filter element is the "stock" Racor PS120 screen that came with the filter, and which many people on here use. It is not clogged.

I did not open or disturb anything other then the pump itself, and the connection into and out of the pump. As I said, on the inlet side, I also tightly clamped off the hose, about an inch from the pump. Plus, I drained the fuel bowl (under hood one), and removed/reinstalled the filter.

The air/foam is occurring on the inlet/tank side. You can clearly see the fuel "splashing" into the pool in the bowl, as it comes in from the tank. The fuel level in the bowl is only about 1/2 to 2/3rds full, with the rest air and/or foam. It does seem as though the pump is pulling fuel faster then the bowl can fill. As soon as I shut the truck off, the bowl fills up.

I think, due to a combination of installed height and angle (in relation to the tank and the fuel pump), as well as the height/relationship between the inlet and outlet fitting on the Racor, I think I may have an air pocket trapped at the top of the filter housing. Previously, with the old pump, I eliminated the air by alternately shutting off the inlet and outlet valves, for 15-20 seconds at a time, with the truck running. This allowed the pump to suck a vacuum and, I think, pull trapped air out; eventually getting the bowl/housing to fill to the top ( or at least to the level of the outlet). I tried this yesterday, and it seemed to start to work. However, the pump would "scream: and make a buzz saw sound the second I shutoff fuel flow. I'm afraid to kill a brand new pump, by essentially running it dry. Even if that procedure works, I shouldn't have to do that to not have air in there. Something isn't right.

 

Your filter media is fine... NOT too tight at all!

If the elevation of your PS120 housing is too high, you have simply trapped air with no way to get it out.

To test this out, and for a short term solution... IF you have the room... unbolt the filter unit completely from its bracket while the truck is running, and SLOOOOWLY lower it closer to the ground so that the air can begin to get sucked upwards towards the pump inlet (assuming you can drop it down low enough for that geometry). Once the air is evacuated, push the filter back up to the bracket and re-bolt it in place.

If the above works, you're going to have to drop the Racor mounting lower so that you don't re-create the situation in the future.

Alternatively, you can install a tee on the inlet side of the PS120 filter with some form of vertical vent line. This vent line can tie into the vent line on top of your tank (as long as an open vent remains in place), or into your vent line attached to the tank filler tube, or you can even just put a small valve or fitting which would allow you to vent the air anytime necessary. The safest thing, if you run a vent line, is to run it high enough above the tank so that is can just stay open all the time (just like your tank vent), and the fuel filler tube vent line is the easiest one to connect to in that regard.

 

Not sure if I am missing something here but are you still using the stock "quick connect" fittings between the tank and Racor filter? If so that could very well be your problem, especially with the high flow pump.

 

That's exactly what I was thinking. I was planning on using the other plugged outlet port on the housing, since it it higher then the inlet. My Racor is on the OUTSIDE of the frame rail, whereas many have put there's inside the rail, so my inlet/outlets are reversed.

EDIT: OK, WTH??? I just tried twice to make a simple diagram with various symbols, of my inlet dn outlet config, but the forum keeps deleting half of it?????

 

No. I cut a whole in the bottom of the tank, and installed a FFD bottom feed sump. I have an aluminum "growth" on the bottom of my fuel tank, which is connected to my Racor with 3/8 rubber fuel hose and barbed hose connections/clamps. The filter is connected to the pump with 5/16 rubber hose.
The OUTLET of the pump (pressure) is still connected with the factory QC and braided line to the motor. The factory RETURN line is still connected. I did NOT drop the tank. I simply bypassed and abandoned-in-place the factory pickup/Q.C.











ALL connections/fittings have since been encased in black RTV, even if these pics don't show it.

 

your symptoms fit with a what faulty CPS can cause, you are getting a CPS code , I would resolve the CPS code before I worried about looking elsewhere for the cause of your issue.

Ya, I read you have tried 3 different senders and a new pig tail. I don't have any experience with the CPS system other then changing the sender but if I were you I would look deeper into it, obviously something is causing the code, figure out what it is and correct it. Maybe you will get lucky and it will also clear up the issue you are chasing.

 

I only recently got a cam sensor code, and it only happened twice, at full throttle and high rpm. The problem has existed long before I got any code. The cam sensor code may be a "red-herring". It may very well be an effect as opposed to a cause. In other words, something else causes the motor to slow/stutter. This will abruptly change the signal coming from the CMP, "fooling" the computer into setting a CMP code. Maybe????? I don't know.

I'm so disgusted with this thing, I don't even want to work on it. I'm also pissed that when I'm finally willing to let some overpaid grubby little mechanic put his hands on it, they aren't any that have a clue what to do with it. The dealer gets $120/hr. What are they smoking? Yes, I know its "industry standard rates" now, but it shouldn't be. Even half of that is pushing it.

 

Ah... you're singing my song. I had to walk away for 9 months before I could come back swingin' away at "Stinky" with a wrench. I nailed it in one, after the respite.

I know how this works - I fried my brain for 2 years straight before I got everything under the hood right. It's really just back away and answer two questions.


Cam Position Sensor code only shows up when the Camp Position Sensor signal doesn't get where it's supposed to - when it's supposed to. The question - OEM or aftermarket CPS?

Air in fuel strainer housing: The pump can not introduce air in the fuel - it's sucking through there, not blowing. The OEM pump was offering up 42 PSI Fuel Pressure, the new one goes to 62 PSI and parks (pressure regulator there). This means the new pump is pulling more flow, but we don't know how much more flow because the regulator is now returning all the excess to the tank. There it is - the regulator is now returning all the excess to the tank - including any air in the line. Where is your pickup in relation to all that splashing around by the fuel regulator return?

 

Unfortunately, I can't just walk away and wait. I NEED this thing to work, yesterday.

Both. So far, one oem- used in the truck when I got it (grey "recall"), and 2 different aftermarket (1- Standard PC139 - for OBS) and (1- NAPA Echlin CSS1103 - correct for '00). I have a new Motorcraft grey I may try. In a lengthy conversation with Jody @ Dp yesterday, he mentioned the possibility of the cam gear walking. However, none of my sensors have any physical damage to the tip. Also, as I pointed out, and he agreed with, it would seem that if the cam gear walked at 2100-2400 rpm, then why wouldn't it continue to do so at higher rpm? If I run it past the problem area, it clears up. I can hold it at 3,000 rpm with no problem.

Not quite. Old pump was 58psi at idle, down to about 42-45psi at WOT (trying to read gauge throw the windshield and sideways with sun glare)
New pump is 62psi at idle. No data at WOT.

Next point... HMMMMM......... See my pictures posted a few posts up. The bottom sump is directly below the factory pickup foot. Or, rather, where it used to be. It was in my way, so I cut it off. I kinda wish I hadn't. That said, the tank is full right now. So, that aerated fuel would have to plunge the full depth of the tank, with the entrained air bubbles remaining intact, pushing aside about 30 gallons of diesel and forcing its way into the sump/feed hole. With a nearly empty tank, I could see it. With a full tank, it seems implausible.
I'm wondering if I should forget about the cam sensor for now, and get the air taken care of. Now that I think about this, all my problems started right around when I did the rear leaf springs, and the hangers. The driver side front hanger is next to the tank, and I really started shoving/kicking the tank out of my way as I got more and more pissed, and my hand got more and more cut up trying to get the new hanger bolted in. Maybe I disturbed some o-rings/Q.C. fittings then, and started the whole aeration thing? Of course it doesn't help that the front of the tank is held up with a ratchet strap. Yes, I know.... It's on the list.

 

One other thing - you're running this without the chip until you get all the woes sorted out, right? I don't mean stock tune - I mean no chip. I had a weird issue once, and I tried running stock tune to clear it up - dudsville. Pulling the chip was my only salvation. Of course... that meant I had to drive 400 miles with big nozzles and no tune to compensate. The throttle was a switch - go, idle, go, idle.

 

Ugggg... No...... I just really don't want to mess with it. I can't just pull it out, because of the plastic "box" around the pcm. I would have to unbolt that under the dash, as well as unbolt the pcm firewall connector, to get enough slack. Last time I did that, to update the tunes on the chip (I don't have a laptop), I lost a screw in the e-brake mechanism, and it took me 2 hrs to get it out. It will be even more difficult now, due to my recent clutch pedal mod/fix. The pedal is in the way, but its no longer a simple matter of just popping it off the linkage.

I want to resolve this air thing first. If that doesn't work, then I'll fight the pcm/chip. I suppose I could make the opening bigger, on the pcm surround box. But, then it would no longer "protect" the chip, from getting kicked,etc... under the dash.

So, was your chip damaged/defective when you had that problem?

 

The air is being sucked in somewhere. Mine is mounted as high as I could get it and I don't have any trapped air. I'm not sure he black rtv is a good idea. That just masks the problem. Also the vent hose idea does the same thing.

Looks like the racor caught a lot of tank shavings that you didn't get out after drilling.

 

It was a borrowed chip (long story). The original owner of the chip soldered big mounds on the connector to his PCM. When he installed the chip on his truck, it spread the pins. My PCM has been solder-wicked, that means very flat contacts. I installed his chip on my PCM, and the chip got 400 miles from home before it made the executive decision to fail.


I have since had two PCMs flashed for my injectors. That miserable drive home won't happen again.