Feul head performance appears tied to tranny performance.

turbobill · **Posted:** Sun Oct 23, 2011 2:06 pm

I have had an ongoing issue with air in my fuel head until recently when I replaced my fuel head and installed an inline fuel pump (see my post - Air in fuel filter head). After the pump mod I continued to have occasional issues with my tranny that went away when I bled the fuel head.

My tranny would down shift while I was driving and it would not shift back into OD or lock up. The tranny generally stay in this state until I bled the fuel head.

Now the spooky part. Since installing the lift pump, my bleed pump on my fuel head is rock hard, unless I open the bleed valve. With the pump it is enough to just open the bleed valve, with the pump on or off, and the tranny operates normally again for a few days to a few hours.

My thought was that I now had a fuel overpressure situation so using the Automatic bleeder mod - per BlackLibertyCRD that was sent to me by Papaindigo I installed a full time bleeder system. If my system works out I'll detail it in another post.

I have already had one incident where my tranny downshifted. I tried accelerating and decelerating but no change. Had to stop at a light so I turned off the engine and restqarted. No more issues with my tranny through three short trips.

My old style fuel head was leaking at the heater plug and would build up copious air in just a couple of days. When I changed it to the new style I continued to have similar tranny problems but much less air. The tranny has been the ONLY problem I have had due to air in the fuel head, never problems starting or idling.

So help if you can. What is going on with my tranny? Is there a safety mechanism that is kicking in, a sensor that may be triggering? What is the connection between the fuel supply state and my tranny not shifting into OD? I am really at a loss and could use your help.

Thanks.

Joe Romas · **Posted:** Sun Oct 23, 2011 2:26 pm

Do you perhaps have some type of scanner attatched to you obdii port :?:

turbobill · **Posted:** Sun Oct 23, 2011 3:25 pm

No scanner. I bought the Jeep in November of last year and it ran fine for 6 months then the air in the fuel head issue showed up. It started out as a problem about every 3 to 5 weeks and ended up a daily problem which I attributed to my old style fuel head leaking at an increasing rate. The ONLY problem I have ever had was the tranny issue in not shifting into OD and not locking up. Bleed the head and all was OK again until the next time.

xtriggerman · **Posted:** Mon Oct 24, 2011 11:14 am

It looks like you still have to track the air infiltration problem down. There is a post pictureing the install of a in tank lift pump. Is that the one you installed? I would personaly hard plum from tank bottom to the fuel head with AN6 fittings and line. Those push on O ring connectors in the stock system will leak with the slightest imperfection.

turbobill · **Posted:** Tue Oct 25, 2011 9:41 am

My pump is mounted in my engine bay. I have replaced the push on fitting on the supply line at the tank with a piece of fuel line and hose clamps, I am sure it is not leaking now. If there is an air lead between the pump and the fuel tank it would have to be at the rubber fuel ine connection to the metal fuel line and those look great with no sign of fuel wetting.

I have the fuel head vent removed and have installed a permanent connection between the fuel return and the fuel head so fuel is constantly being pump through the head.

Now I am having a tranny fault where the tranny shifts down less than 1/4 mile from start up. The tranny then will not shift into OD or lock up, it seems as if it is "stuck" in third or fourth gear. If I stop and turn of the engine and restart it then the tranny fault is cleared and stays cleared for how ever long I drive the car. When I stop for more than about 1 hours the tranny fault reappears the exact same way. At least now I do not have to stop and bleed the fuel head, so I believe my purge system is working, just not perfectly.

My question remains - Why do I get this tranny fault? What in the Jeep system causes it? It must be some sort of safety default or damage prevention system in the computer. If I could understand that then maybe I could better understand the root cause of my issue.

Thanks for any assistance you can provide.

turbobill · **Posted:** Tue Oct 25, 2011 2:25 pm

The air in my fuel head problem was initially solved when the fuel pump was installed. I have reviewed all my notes and it appears that the tranny problem reoccured when I reqired my pump according to the schematic from Blackliberty busing the pump prime relay pin 5. This connection provides a cut off of the pump if the ignition switch is turned on but not started, the pump will run 15 seconds then turn off. When the engine is started the connection is supposed to be powered all the time.

The pump seemed to operate as designed.

y r. Gasket pump will not pass fuel when it is not running. I have tested this by unplugging the power on the pump starting the engine and waiting, The engine runs out of gas in a few minutes and shuts down. Hook up power to the pump and all is well again.

S-O-O-O I postulate that this power point has some short term interruption when the intial 15 seconds is up and that interruption is enough to generate what ever fault occurs that causes the tranny to stop shifting into OD.

I tested the theory by hooking the power to the pump to a connection that is powered 100% of the time the ignition switch is turned on. There is o power during AUX operation so I can listen to the radio, etc without running the fuel pump. Since the pump now pumps fuel through the fuel head and back to the fuel tank via the vent port on the fuel head and the fuel return line, no problem with the pump running when the ignition switch is turned on but the engine is not running. Since rewiring the pump I have made 4 trips without any issues from the tranny, a little early to declare 100% victory but 100% better performance than I have been experiencing. Maybe if I had a flow through pump like the faset this problem would never had been evident.

To set up the full time purge I used a 3/8 nylon hose tee from Home Depot and a 10mmX1.25X30mm bolt. I drilled the bolt length-wise with a 3/32 drill using my hand drill and cut off the head of the bolt with a hack saw. I used JB Weld for a thread seal and snugged up the bolt in the vent port on the fuel head. I probably could have shaped a cone on my grinder to seal like the OEM vent valve does but I didn't want to take the time. Used less than a foot of 3/8 fuel line to tap the tee into the fuel return line and connected to the bolt now screwed into the vent port. Total deal less than 2 hours and less than $10.

The Mr. Gasket built up pressure in the fuel head making the pump rock hard so this configuration removes that extra pressure. The pump will probalby last much longer as well since it is not pumping against a strong head pressure.

Interesting project, hope it is done and I can just get on with driving my CRD, now I need to do my 100K maintenance.

xtriggerman · **Posted:** Wed Oct 26, 2011 12:36 am

Thats a interesting story. With as you noted, the lift pump is not a flow through design that could be the weak link in the mod. The old Cummins Carter lift pumps that were used in the Dodge (pre in tank pump) were flow thru when not powered. Those pumps are every where to be found with a idle flow pressure of 13-14psi. A bit expensive at last I looked $130 ish but when mounted off engine will generaly last a long time. Im not sure how these common rail pumps flow their return fuel but the old style pumps benifited from positive in comeing pressure keeping the return flow moving as best it could. That ensured the best cooling of the I pump. I can imagine a constant 20K plus I pump line pressure on the CRD would need a good return flow to manage heat. I hope the forced flow into your return does not inhibit the hot return flow from the I pump. You can get just so much flow threw a single return line and 2 feeds into it. Now if you over size the return line all the way into the tank.... just a thought. But your probably OK as is, just rambling :lol:

turbobill · **Posted:** Sun Oct 30, 2011 1:27 pm

It is a week after my last post saying that my problem was solved by changing the power point for my Mr. Gasket pump. I have had no hicc-cups, nada. It seems to be working just fine. I think the largest restriction in my return line is not the added fuel pressure but rather the tee I put in the line. I was careful to instal the tee flow thru for the rail pump return and teed for the fuel filter return, plus the return from the fuel head is passing a 3/32 port hole now. I think it will be OK, good so far.

Feul head performance appears tied to tranny performance.

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