ISB Fuel Pump -Transfer Pump

[Roadwander]

I have just completed a head gasket replacement on my 99 Coachman Sportscoach 5.9 ISB because of a coolant leak underneath the thermostat housing. It has 45K miles. Now it will not start (it operated perfectly before I worked on it) and I have traced the problem to lack of fuel. Finding no fuel at the injector lines, I cracked the line that goes from the transfer pump to the fuel filter (at the fuel filter inlet) and got nothing when I cranked the engine. It appears the electric lift/transfer pump is inopoerative but I do not know when the lift/transfer pump is supossed to operate. So, I have some questions:

Does it operate during cranking?

Does it operate for a few seconds whenever the key is turned to the "on" position even if the engine is not cranked?

Does Cummins use an Auto Shut Down Relay like is used on fuel injected automobiles? If so, where might the relay be located?

What is the nominal output pressure of this pump?

Lastly, is the lift/transfer pump controlled by the Engine Control Module?

Thanks in advance for your help.

Ken B

[sknight]

Here's how the lift pump operates on my 2001 Dodge with the ISB Cummins.

For a prime cycle, key on, just bump the starter. The pump should run for 25 seconds as a prime. If it ran before but doesn't now then I'd check grounds, fuses and power, broken wires. It uses a fuel pump relay that I believe is ECM controlled.

Chances are your lines are full of air. Loosen all the lines at the injectors and spin it over. You should start getting fuel fairly fast. Don't spin the engine more than 15-20 seconds, and let it rest for at least a couple of minutes.

Once you start getting fuel, tighten those lines up to spec. Once you get fuel at four lines you can tighten the rest up, and spin it over. She'll start, you'll have to keep it running with the throttle until she cleans out.

Hope this helps.

[Roadwander]

Thanks for the response sknight. Yes, my lines are full of air. I removed the injectors, the fuel transfer tubes inside the cylinder head that feed each injector and the complete high pressure fuel line assembly that goes between the high pressure pump and the cylinder head. I got air everywhere - LOL.

It is my understanding that the VP44 high pressure pump will in fact draw fuel from the tank even if the lift pump fails. I hear it is hard on the VP44 pump when this happens but the engine will in fact continue to run with a failed lift pump as long as there is no air in the suction side of the system. What I am saying is that perhaps my lift/transfer pump had failed previously and I was not aware of it? My lift pump doesn't seem to be operating at all - - not during cranking, not after a bump crank or not by cycling the ignition switch. I'll get out my volt meter tomorrow and see if there is voltage to the pump during the times you indicate, Thanks again for your information. Ken B.

[sknight]

So far as I know it won't run with a dead lift pump, but I'm also a GM diesel tech, so I don't know the intimate details. Yes, I have a Dodge that I bought while at GM. Drive the best, work on the rest.

Check at the pump, then go straight for the fuse and relay. Those are the easy parts, then see about the wiring. But if you're competent enough to replace the head gasket, you probably already know that.

If you're in Ga. I have a pump you can try.

[RustyJC]

Yes, the ISB will run with a dead lift pump, but the VP44 injection pump will soon fail as it uses the excess fuel delivered by the lift pump for lubrication and cooling. Anything less than 8 psig at the VP44 inlet will shorten its life. A healthy lift pump will put out ~15 psig at idle and ~12 psig at full throttle.

Rusty

[EngineerMike]

The operation cycle on my old 6.5 GM Trek went like this:
Key On- ECM powered a combination mechanical/electric relay for a given cycle of seconds, relay powered the Lift Pump
Start- oil pressure closed the mechanical feature on the m/e relay to continue powering LP during operation
Key Off- cut power to a fuel solenoid on the Injection Pump killing fuel to the engine; oil pressure dropped when engine died opening the m/e relay killing LP
Get in a Horrible Wreck that Kills Engine & Oil Pressure- m/e relay kills LP (no oil pressure to keep relay closed) so no fuel continuously pumped out onto the potential fire after the wreck.

I thought the m/e relay was a stupid setup that should have been run by the ECM full time, but was corrected by a wiser man- the safety feature is apparently a fail safe set up by SAE as a standard method based on a lot of field experience. I think our rigs are managed the same way.

If you can put a vacuum pump on the fuel line between LP & IP, you can probably draw fuel past the LP and get it primed again, then use it to prime thru to the injectors. If you have no 12V at the LP then the relay powering it for startup is not working and you need to isolate & fix that. If you have been running for some time w/out a working LP, then the price is heavy wear on the IP as cited above; You may be able to check on that if there is a way to check injection pressure delivered (maybe on the common rail if yours is electronic?).

[RustyJC]

A trick used by the Dodge guys to push fuel to the injection pump is to cut a hole in a tennis ball and run a compressed air line through the tennis ball. Hold the tennis ball on the fuel filler pipe and pressure up the fuel tank with compressed air. This will force fuel up to the lift pump and injection pump. The vent line in the Dodge trucks has a check valve to let air in as fuel as used, but will not let the pressure out.

The stock injectors are not self-bleeding, so you may have to crack the fuel lines as described above to get fuel to the injector cross tubes. It will take quite a bit of cranking to get the engine to fire, so be careful to let the starter cool between cranking cycles.

Rusty

[sknight]

Quote:

Originally Posted by RustyJC A trick used by the Dodge guys to push fuel to the injection pump is to cut a hole in a tennis ball and run a compressed air line through the tennis ball. Hold the tennis ball on the fuel filler pipe and pressure up the fuel tank with compressed air.

You have to prime a Duramax the same way. Takes quite a bit of air pressure on a GM too, more than you would think. I have a low pressure regulator that I'd have to turn up to about eight PSI to pump out a tank that had gotten gasoline in it. Not a happy feeling putting a plastic tank under that much positive pressure the first time either.

[Roadwander]

After a little searching, I found the problem. In addition to the heavy duty cables, I have four separate ten gauge wires coming off the positive side of the battery. I had only three connected as one had dropped down behind the batteries and was hidden from view. Early in my working career I was an autoshop teacher for almost a decade and used to tell my students to not over analyaze and to always check the simple things first - - guess that statement came home to roost, huh? LOL.

Also, the electric transfer pump runs for about 15-20 seconds after the starter is bumped. It does not operate if the key is only turned to the run position. The pump will continue to operate for 15-20 seconds even if the key is immediately turned off after bumping the starter.

Although I cannot hear the pump with the engine running, the pump is quite noisy when the engine is stopped. It really makes a loud buzzing sound after the starter is bumped, so if there is no buzzing noise after bumping the starter, then the pump is probably not operating.

Thanks for all the help. Travel often and travel safe. Ken B

[sknight]

Same way the pump on my 2500 works, and mine raises Hell when the engine's off. Glad it was an easy fix.

[BigFun]

Being a previous 24 valve ISB owner in an 01 Dodge, the lift pump is definitely the weak link. Many replaced the OEM pump with a FASS. Heavy duty with filtration built in. Spendy but a good investment. Bill Kondolay of Diesel Transmission Technoligy (DTT Performance Diesel Transmission and Power Accessories) has/had a mechanical pump which attached into the serpentine belt system that seemed like a smart design and worth looking at.

Bottom line is to gauge that fuel pressure from the lift pump. Fuel pressure gauges are inexpensive and will alert you to low pressure soonest. Easy to install too.

Hope this helps!

BF

[rharveysr]

Been using the FASS pump as our replacement pumps offered to our customers. Mounted back next to the tank is much easier on the pump to push fuel than pull fuel. The 3/8" lines that come with the kit helps keep that VP44 happy.
Last hotrod project that we did...all the feed lines were replaced with 1/2 steel braided lines with Earls fittings.

Rick

[Ray,IN]

While you are delving into the lift pump, replace the flexible lines to the pump. They have a penchant for failing internally (collapsing), yet appearing fine on the outside.