How does one tell if a primer pump is bad?

scoon · **Joined:** Mon Sep 10, 2007 10:05 pm **Posts:** 4

Hey there,

I am getting ready to retire my '94 Cherokee and am shopping for a Liberty CRD. I have been reading posts about how some have been fixing the fuel head issues. In one thread I read, a poster wondered if the fuel head problems were caused by users over zealously pumping away at the primer and breaking it. Could someone weigh in on this? How could someone, a buyer like me, tell if a primer is AFU?

Thanks.

Joe Romas · **Posted:** Sat Jan 10, 2009 7:08 pm

The owners manual warns you not to pump it too hard or it will brake :lol:

What you want to be concerned about is if the filter head is leaking around the heater plug.
A list member or two advocate pushing the primer pump too hard to make the heater plug leak :shock:

Adding a lift pump, most have chosen the dodge/Cummins in tank pump, cures problems that a lot of crd owners have had. Some have not experienced problems...yet :lol:

Thinking is air builds up in the highest point in the fuel system and on the crd that's the filter head. This causes the fuel heater and plug to overheat and melt or burn the connector :oops:

A lift pump minimizes or eliminates the air buildup. The symptom I and other have had is after moderate excelleration to say 54 MPH then letting off the peddle enough to maintain that speed the CRD will act like it's running out of fuel. There are other symptoms too.

warp2diesel · **Posted:** Sat Jan 10, 2009 7:28 pm

The Liberty CRD lacks one component that many members including my self along with the Bosch Staff who wrote the book, "Diesel Engine Management" , a lift pump. Since it does not have a lift pump, any place that the fuel system can suck in air between the CP3 pump on the engine and the fuel tank will suck air. The air rises to the top of the filter head where it collects, then the fuel heater is not immersed in fuel as it was designed to be and burns up. I gets so hot that the two leads going to the heater plug located on the drivers side of the filter head melt the plastic and you have another air leak that will cause problems since diesels do not like air in the fuel system.
If you want to see if the filter head is leaking, pump the primer up, use a 7/16" or 11mm wrench and crack open the bleeder on the passengers of the filter head to let out the air and close the bleeder. Keep repeating until no more air comes out. Now press down hard on the primer and hold it for a couple minuets. Then unplug the heater plug, if it is wet, the heater has totaled the heater assembly.
There are some members that swear on a stack of Bibles that the lift pump is not needed and they have not had a problem. I along with many members do not agree with them.
If you install a lift pump even the cheep Carter I put on mine and you have a good fuel filter head, it will work for a long time. Are there other better fuel filter heads out there, yes there are.
Other things you need to do are: 1) Do the ORM and make plans for the SEGR kit installation. 2) Clean the MAP sensor. 3) Install a Provent or TDI guy to remove the oil mist coming from the blow by.

Good Luck

ATXKJ · **Posted:** Sat Jan 10, 2009 9:28 pm

What you need to look for is the Heater plug leaking diesel
diesel is a lot bigger molecule that air so if it's coming out - you know air is leaking in when it runs.

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=35702

heater is the plug on the right.

scoon · **Joined:** Mon Sep 10, 2007 10:05 pm **Posts:** 4

Thanks for the replies. I'll be checking the heater plug for leaks.

Thanks.

nursecosmo · **Posted:** Sun Jan 11, 2009 7:40 am

ATXKJ wrote:

What you need to look for is the Heater plug leaking diesel
diesel is a lot bigger molecule that air so if it's coming out - you know air is leaking in when it runs.

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=35702

heater is the plug on the right.

Hey ATXKJ, Did you get a new avatar or did you already have that one?

ATXKJ · **Posted:** Sun Jan 11, 2009 8:29 am

nursecosmo wrote:

Hey ATXKJ, Did you get a new avatar or did you already have that one?

a couple of weeks on this one -
I had another that was similar but with the Mountains in the background
(both from Moab 07 - CaKJFreedom)

nursecosmo · **Posted:** Mon Jan 12, 2009 1:23 am

ATXKJ wrote:

nursecosmo wrote:

Hey ATXKJ, Did you get a new avatar or did you already have that one?

a couple of weeks on this one -
I had another that was similar but with the Mountains in the background
(both from Moab 07 - CaKJFreedom)

Groovy

UFO · **Posted:** Mon Jan 12, 2009 1:25 am

I broke my primer pump. You can't get all the air out of the filter head like before. But it purges enough as it hasn't (yet, touch wood) shut me down.

onthehunt · **Posted:** Mon Jan 12, 2009 6:09 am

You don't need to touch the pump unless you change the fuel filter. If you do, you have an air leak. If you have an air leak install mentioned fuel pump and cover it up.
Then log back on here and tell everyone how that pump fixed all of your problems and it runs soooo much better. Don't forget to quote something smart from a Bosch diesel book and tell the CRD engineer that he doesn't know what he's talking about.

On second thought forget all that and just drive the thing. You will know if something is wrong.

UFO · **Posted:** Mon Jan 12, 2009 7:01 pm

onthehunt wrote:

You don't need to touch the pump unless you change the fuel filter. If you do, you have an air leak. If you have an air leak install mentioned fuel pump and cover it up.
Then log back on here and tell everyone how that pump fixed all of your problems and it runs soooo much better. Don't forget to quote something smart from a Bosch diesel book and tell the CRD engineer that he doesn't know what he's talking about.

On second thought forget all that and just drive the thing. You will know if something is wrong.

This is not accurate. If your fuel filter is slightly plugged, you will have a partial vacuum at the top of the fuel head and all the dissolved air in the fuel will collect at the highest point. Even "leak-free" fuel systems do this normally, and VW and Mercedes both bleed this high point back into the fuel return. This is the major error DC made in the fuel system design.

gmctd · **Posted:** Mon Jan 12, 2009 7:25 pm

warp2diesel · **Posted:** Mon Jan 12, 2009 7:34 pm

onthehunt: You know that certain mental disorders that result in suicide can be treated with B complex vitamins. The substance in your signature line is rich in vitamin B complex. Parts of the world where the substance in your signature line is not available have a high number of suicide bombings. I would conjecture that if the substance in your signature line were available chances are that the suicide bombings would greatly diminish.
Since you never want to agree with any thing I post, I wanted to post something you could not disagree with.

Go have a beer and get the B complex you need.

I do not miss using the hand primer when I replace my fuel filter, I just crack the bleeder and turn the key, how simple.

To vent the small bubbles in the fuel system, I crack the bleeder with the key on, how simple.

gmctd · **Posted:** Mon Jan 12, 2009 7:39 pm

1. The Bosch manual indicates a remote auxilliary lift pump supplying the CP3 thru a filter
a. The Bosch manual does not specify minimum heighth above or distance between supply tank\lift pump, filter and CP3

2. The KJ CRD, with it's short wheelbase and compact fuel system, likely does not require, nor does it have, aux lift pump
a. The Bosch CP3 ECM has integral aux electric lift pump logic, plus hardware execution to control an electric lift pump

3. The KJ CRD was manufactured with no aux electric lift pump
a. The KJ CRD power and wiring system has fully functional lift pump fuse, relay and wiring

4. Diesel fuel systems require filtration - those without aux lift pumps also require a priming pump to move the fuel
a. Fuel filter\priming pump should be located as close to fuel tank level as practical to prevent gravity drain-back

5. The compact KJ CRD has little space in engine bay for filter and priming pump, so filter is squeezed in on firewall
a. Location on firewall is ~one foot above fuel tank, ~two feet above fuel pickup in bottom of tank

6. Most KJ CRD's suffer from gravity-induced fuel drain-back at engine-off events, some to greater extent than others
a. DCJ installed pressure fittings in fuel lines between tank and filter, which needed vacuum-service fittings

7. Fuel being denser than air, seldom leaks by those fittings
a. Air, being somewhat less dense than fuel, often leaks into those fittings

8. Fuel, being heavier than air, often bleeds back down from that two foot height advantage above fuel tank pickup
a. Air, being lighter than fuel, often bleeds up toward that two foot height advantage over fuel level

9. Fuel filter\manager head, now being full of air, rather than fuel, presents unique scenario for the fuel heater
a. Fuel heater element, being designed to heat denser fuel, heats itsownself into immolation, cremating surrounding plastic acouterments

10. Fuel primer pump, priming into compressible air, rather than non-compressible fuel, may now be destroyed in repeated priming frenzy, trying to recover that which was lost due to air leak(s) in fuel supply line
a. Easily noted by raw fuel dripping from cremated heater-supply connector, particularly at priming event, if primer still works

Would rubber hose and clamps on fuel line remedy this?

Would aux electric lift pump remedy this?

Is Rachel Weiss hot, or what?

Questions, questions..................

UFO · **Posted:** Mon Jan 12, 2009 7:54 pm

gmctd wrote:

Is Rachel Weiss hot, or what?

Questions, questions..................

HOT!

scoon · **Joined:** Mon Sep 10, 2007 10:05 pm **Posts:** 4

Hmmmm. I sense a great amount of tension about the quality of the fuel head and fuel delivery in the CRDs.

ATXKJ · **Posted:** Mon Jan 12, 2009 10:01 pm

not a great deal of tension - stock is bad. The appropriate fix is sometimes a discussion.

the best combo is a in tank lift pump (Cummins) and a Racor (metal not plastic) fuel head - with 2 micron filter

however the Racor should be done after Warranty - because the dealer can see it
since the dealer are clueless about troubleshooting - anything visibly different is pointed to as the root cause of all problems.

gmctd · **Posted:** Mon Jan 12, 2009 10:02 pm

If you had a V6 gasser (patooie!) KJ, you'd sense a lot of tension in the ignition circuits: high tension..........................

mackruss · **Posted:** Tue Jan 13, 2009 12:36 pm

onthehunt wrote:

You don't need to touch the pump unless you change the fuel filter. If you do, you have an air leak. If you have an air leak install mentioned fuel pump and cover it up.
Then log back on here and tell everyone how that pump fixed all of your problems and it runs soooo much better. Don't forget to quote something smart from a Bosch diesel book and tell the CRD engineer that he doesn't know what he's talking about.

On second thought forget all that and just drive the thing. You will know if something is wrong.

Before i joined this forum, i did't even know that there was a primer and that was after 60000 miles of motoring with no shudder or anything else fuel pump related. After realising what the primer was for i became absolutely paranoid over potential air in the system as explained by all the fuel pump addicts. I proceeded to prime on a weekly basis and bleed and then i realised that if i continued to do this i would end up with an air leak in the fuel head due to worn components from continuos priming that was not neccessary in the first place.

Yes i had a firm primer when my pump was still fitted however in the back of my mind was the fear of doing some kind of damage to the existing CP3
even at a low pressure and because i do have some faith in the design engineers and that between them and Bosch, how bad a decision was it not to install a lift pump.

The 55 mph shudder that is / was prevalent due to air in the system and then disappeared after installation of a fuel pump has now been superseded with a potential transmission problem and at the same 55mph or thereabouts.

Fit the fuel pump and the engine runs quieter, smoother and better throttle response is a load of crap. You got an air leak, find where the leak is and fix it otherwise don't look to fix something that aint broken.Yes, it's easier finding a leak with positive pressure in the fuel system but what percentage of CRD's have this problem. Yes, the engineers that are constantly under the whip for cost cutting left the wiring harness in the CRD's and the relay but aren't they all running off the same line as the petrol versions are or must they fit a relay box designed specifically for the diesel and charge the consumer more.

Now i'm pumped..

gmctd · **Posted:** Tue Jan 13, 2009 2:59 pm

The petrol (patooie!) version PCM is a Mistubishi-based DCJ product, conceived and written by DCJ to control an electronic fuel injection system, with logic for an electric fuel injection pump as required by that EFI system, so naturally the fuse, relay and wiring sufficient to accomodate installation - the PCM also has integral Mitsubishi-based transmission control, harness co-mingled with EFI wiring

The Diesel version ECM is a Robert Bosch GMBH product, conceived and written by ole Bob specifically to control the CRD engine - integral is aux electric lift pump logic, having nothing to do with the petrol (you know!) version - odd that Bosh would indicate aux lp is not needed, then write-in logic routines specific to controlling an electric lift pump, eh - automatic transmission control is relegated to the separate and stand-alone TCM, clear across the engine bay on the opposite fender, with it's own wiring harness

Even the lighting harnesses, which should be identical, are not similar due to CRD-specific lighting position\locations

Many changes and alternate paths differentiate the petrol (!!!!) version harness from the Diesel version, so yes, there are separate wiring harnesses for each

How does one tell if a primer pump is bad?

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