As the temps have dropped, I'm having trouble starting my truck. So I topped up the battery fluid (deionized water), took apart and cleaned the terminal connections, installed 2 battery blankets and had it warming up for 2 days now (including the block heater). Went to start it after cycling the glows plugs twice, very little cranking power.

Put the charger on it, needle is fluctuating wilding ... regardless of which battery I hook up to. There is a loud vibration noise coming from the cylindrical

component that my orange trouble light is touching when the glow plugs are cycling. The noise stays for a while (30 seconds, then goes away, then comes back. It even does it after the GPR has cycled.

What is this component called? What does it do? Does it affect the start-ability of the diesel engine? How do I "trouble shoot" it? (be gentle ... electrickity is not my thing).

 

Vacuum pump!

ESOF is switched on and off via the vacuum in the reservoir, which is generated by the pump.

HVAC venting directions are controlled by the vacuum in the reservoir, which is generated by the pump.

If it is continuously running, you have a leak somewhere. I had a very small pinhole leak in the small red tube that comes off the reservoir that took me over an hour to find. Alot of times the rubber hoses running to and from the reservoir to the hubs or into the cab will deteriorate and leak. You can see if the pump is good by removing the single connection to the reservoir, putting your finger over it to cap the pump off and see if it shuts off after a few seconds. If it does, then work your way through the tubes and system until you find where the vacuum pump still runs. Your leak will be in that leg.

Your in luck, no real electricity in this system, just air and you should be very familiar with air.

 

That is your vacuum pump. After it cycles off it should not come back on for quite some time, mine is like 30 minutes but my hubs have been disconnected from the system.

 

Thanks guys. I've never heard it before ... ever. There is a little whirling sound I hear which I assumed was the fuel pump priming up.

Does the vacuum pump affect the starting system in any way? I assume the answer is no but I need to ask. Also, if the vacuum pump is making this much noise (and it is loud), does that mean it is going or is gone?

 

The guys above are spot on. If it does indeed cycle off. Your the lucky one. I call mine the breast pump. It's always sucking. I switched to manual hubs and plugged the lines. I worked out leaks and worked on the hubs until I got over the whole "having to anticipate whether they would indeed work when I needed them type of deal".

If the hubs are locking and the Heater is behaving, everything is as designed.

Denny (Go buy a lottery ticket now)

 

No, other than a minimal draw of power from the batteries while the vacuum pump is running and you are waiting for the GP's to kick off or for them to warm up. It should turn on after the truck has been sitting for a bit, but should turn off after the reservoir is at vacuum capacity. It will cycle on sometimes, but not often.

If it is running constantly, you have a leak.

If it runs, then shuts off for a minute or 30 seconds, you have a leak.

If it runs, then shuts off for a few minutes, you have a leak.

If it runs, then shuts off for 30 minutes or so, then you are good.

There are only a few hoses/connections coming off the pump/reservoir system. Not a difficult part to troubleshoot, once you see the route of the lines. Again, I would first remove the hose going from the pump to the reservoir and put your finger over that hole on the pump. It should stop in a very short period of time since it has built a vacuum pressure. If it does shut off, you know your pump is good and your have a leak in the lines somewhere, which on a 20 year old truck is not an uncommon thing.

 

Thanks for the laugh!! Mines been a breast pump a time or two.

 

I'll throw in my .02 and experience. The pump is meant to cycle infrequently. It is not designed for continuous use.

I killed one that way with a vacuum leak (turns out those rubber vacuum caps don't last forever). I kept hearing the pump running but since my ventilation was working fine I put it on the backburner "until I had time to get to it." Pump died and the vacuum leak moved to the top of the list (summertime) and I magically "had time to get to it".

If it's running all the time then it shouldnt be any further than the ESOF solenoid. If nobody has been in the passenger's seat kicking under the dash it's probably not there (it could be but unlikely). Most likely it's somewhere between the firewall, pump, reservoir, ESOF solenoid, or any of the tubing that connects those things. Oh, yeah, check any caps you might have on the system. Those have a tendency to age and split.

Don't be me. Find the leak. If you think otherwise go price that little pump. An el cheapo one will run you over $70. Add $50+ if you want to go Motorcraft. If you do get another pump read the fine print...some are remans.