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Old 04-27-2008, 03:55 PM   #1 (permalink)
seo
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3208 Cat fuel system problem

Hi,
I have a 1982 Ford LN8000 truck with a hydraulic boom on it, powered by a Cat 3208 NA, 5-2 manual transmission. I don't use the truck in the winter, and it's just coming out of storage now. Last December I needed to pick up one last thing, and tried to start it. For the first time ever, it didn't pop right off. I tried some ether, but that didn't help.

I have been told that these engines have problems with their fuel lift pumps, or a check valve in the pump. Is the lift pump part of the injection pump? Or is in that suction/return manifold on the aft end of the right cylinder bank?

In order to make sure that I was doing a good job of getting air out of the system, I rigged up a air mattress inflation hand pump to the truck's fuel tank vent. By putting some pressure on the tank I was able to force fuel all the way up to the fuel filter fitting on top of the left cylinder bank. Between the air pump and the fuel primer pump I was able to get clear fuel running out of the bleeder tap on top of the injection pump, and out of the injector lines when I cracked the nuts on top of the injectors. BUT IT STILL WON'T START. I hate it when that happens.

I have noticed that it looks like theres supposed to be a gasket or o-ring between the primer pump plunger and the pump body, so that there's a good seal when the plunger is screwed in to its storage position. Is this critical? I don't seem to be getting aerated fuel after cranking the engine, but I might be missing something.

Also, I've been told that the solenoid on top of the injection pump is the engine shut-off, and that this might be in the "kill" position. I've certainly seen this happen on engines with manual "kill" controls. Can I just remove the solenoid (how do I do that?) to see if it will run without it, or does it stick into the fuel pressure gallery?

Thanks in advance for any good advice.

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Old 04-27-2008, 08:39 PM   #2 (permalink)
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Here is a pic of the solenoid:
CAT 3208NA NEW STYLE FUEL SHUT OFF SOLENOID WIRING photo - iamflagman photos at pbase.com

The engine won't start if it is bad. You should be able to hear it click
when you turn the key to the "on" position. If it doesn't click when you first turn the key, test the voltage and inspect the wiring, if voltage is good I would say it's shot. You may need a second person to turn the key when you listen for the click with the hood up, especially if you have buzzers or alarms that come on with the key.
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Old 04-28-2008, 05:23 AM   #3 (permalink)
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Hi RMR,
Thanks for this response. Do you remember if the solenoid's actuator rod was in (retracted) or out (extended) when you got it out of the box? If my take on the photo is correct the solenoid actuator rod is normally extended, and retracts when power is supplied. Is that right? Because if so, then if I remove the solenoid that's on there now, the engine should run if the problem is the solenoid.
Yes I'll certainly need a second person or a jumper wire to test the solenoid. The air brake pressure alarms are loud enough that you couldn't hear a nuclear war going on.
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Old 04-28-2008, 07:36 AM   #4 (permalink)
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Those aren't my pics, I don't remember which way the rod goes when energized. In my experience it has been wiring problems, I've never had this solenoid go out,,not to say they don't. I don't know if it will run with it removed.
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Old 04-28-2008, 03:41 PM   #5 (permalink)
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I spent a couple years working on boat machinery and wiring. The basic tool for wiring was a brass wire brush for cleaning up corrosion on contacts, and a tube of dielectric grease. I think the stuff I used was called trailerlite, or some name like that.
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Old 04-29-2008, 05:24 PM   #6 (permalink)
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Finally, something to give back!!!!

So I have a 3208. I gotta keep this quick, since I'm on the clock.

I guess from running too much bio, and too little fuel through my truck overall during too long of a time period, I apparently picked up too much moisture in my fuel.

This caused my IP to stick closed. I mean, fuel shutoff solenoid was no help.... since the lever that the solenoid actuates was stuck closed (which is what I deduced - read on).

Back to my "learning moment". When my truck didn't run last year, I noticed it was a fuel issue. So, I replaced all of the fuel lines from the lift pump to the IP. Still, no love. New fuel filter, topped off and primed. Zero. I then thought of the solenoid.

Inside the IP (again, this is what I learned later on in my activities), there is a lever that naturally slides on a chromed rod with each rotation of the compressor (I think of the IP as a mini-engine-in-reverse, which is what it looks like when you take the cover off). The solenoid, which needs a 12v feed AS WELL AS a good ground connection to the terminal (grounding the case is not enough), naturally pushes down on this lever to stop the flow of fuel (spring loaded). When energized, the dowel is sucked into the body, allowing (IIRC) the next revolution of the engine to push that fuel-stop mechanism vertically up, allowing fuel to flow.

This means that you can remove the solenoid to get the engine to run... in theory. When I removed the solenoid and tried to get the engine to crank, the only concern is that under any sort of runaway condition, you'd be lucky to make it to a bunker before the shrapnel hit. That's conjecture (and perhaps a bit melodramatic, honestly), but I don't like to be without a failsafe, and removing that solenoid and running the engine (with or without governor, that just reminds me of a gun "safety") felt a bit sketchy to me to be trying this.

Still, my runaway engine concerns notwithstanding, I removed the solenoid. And yet, still, no firing.

This is when, upon closer inspection, I realized that the fuel lever, underneath the solenoid dowel, was not moving up. Or if it was, it wasn't taking the rest of the works with it... I could sort of feel a lack of movement, like, even though I could pull the lever up from the hole created by the missing solenoid, it wasn't really *doing* anything. Sort of like a locked car door handle will move by itself, but you know it's not engaging the door opening mechanism.

I figured, the only way to get the truck to move, at that point, was to remove everything from the top of the IP, pull the top cover, and figure out what's not moving inside. Upon doing so, I was able to manually cycle the little wishbone-like lever system that allows fuel to flow. This mechanism is just in the aft side of the IP, and on mine, was stuck, with very slight but noticeable gumming on the interior machined/chrome surfaces of the IP, and corrosion on the cast iron items. By cycling it this mechanism by hand, I unstuck the IP enough to get fuel to flow.

I have since talked to an old Cat service/salesguy, who mentioned that, and I quote, "If you spit on the ground next to a fuel tank on Cat 3208, you need to run a water seperator." Well, I essentially run TWO, and I still had issues... I think this was because of my use of Bio, which basically entrains water into the mix.

Anyway, getting back to my truck, I sometimes notice that this mechanism retains its stickiness. I have a remedy - I will place a 12" long wood block on the cover of the IP, and with the fuel solenoid energized, rap on the wood lightly with a hammer or a rock. Whenever I do it, it looks terrible, but doing this tends to work.

I hope this helps,
Bob

Last edited by Trango; 04-29-2008 at 05:29 PM.
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Old 04-30-2008, 12:35 AM   #7 (permalink)
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I'm thinking that the solenoid extends to shut off and retracts to turn on. A 3208 at work wouldn't shut off, so the mechanic took the solenoid off and took a screw driver and pushed something on the IP pump down. Off she went....... That's what comes to mind.

It wouldn't hurt to take it off and look. All you need is 12V to it to test. Heck, try to see if it will start. If it does, then you know the problem lies in the solenoid....

One time I had a issue w/ my 3208. Sat a while and fuel drained back, I guess. I primed the fuel system till I felt resistance (didn't open anything) and tried to start. Fired right up......
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Old 04-30-2008, 09:01 AM   #8 (permalink)
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Quote:
Originally Posted by Kaliburz View Post
I'm thinking that the solenoid extends to shut off and retracts to turn on. A 3208 at work wouldn't shut off, so the mechanic took the solenoid off and took a screw driver and pushed something on the IP pump down. Off she went....... That's what comes to mind.
Yes, this is the case. The solenoid, when energized, retracts. When not energized, a spring loaded dowel pushes down on the fuel stop lever inside the IP.

The mechanic, FYI, could have also used his finger.... that fuel stop lever is accessible through quite a large aperture in the IP top cover, exposed when you remove the solenoid.
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Old 04-30-2008, 10:00 AM   #9 (permalink)
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Kaliburz and Trango,
Thank you both for your comments.
I think that a basic fact of life for machinery in general, and engines in particular, is that it does them no favors to let them sit around. I'm curious how much Trango's engine runs in a year. If it's a back-up truck that gets started every few weeks, that could possibly explain the gumming up.
The truck that my 3208 is in is an LN8000 boom truck, and the 3208 runs the boom's hydraulic system through a pto. My first thought on getting the rig was to figure out some small auxiliary engine to run the pump. Now I think that it might be a saving grace, because even if it's just idling most of the time that the boom is working, at least it's running.
I don't understand how this style of injection pump works, where it really isn't necessary to fully purge the injection lines to prevent an airlock. I was brought up around machinery with Bosch style pumps (1940's and 50's Cat) and with them you bled the injectors by rolling the engine, and if there was air in the lines, you didn't get injection. Detroit 71's were the first engines I saw that would purge themselves if they could start. But that was because they had unit injectors, and no high-pressure injection lines.
But with this 3208, like Cat 33 and 34 series, if you crack a nut on an injector with the engine stopped, and then work the priming pump, the fuel runs out at the injector. How does low pressure fuel get past the pump plungers?
The thing that I don't like about the fuel system in this truck is that the entire fuel system is under suction right to the injection pump (IP). I prefer a system with a seperate fuel transfer (lift) pump, either an AC type diaphragm or a gear pump like you find on Detroit, Cleveland, EMD. That way the filters and distribution lines are under pressure, and any defect causes a fuel leak out, rather than an air leak in. With an AC pump, there's usually a little lever on the pump that you can work by hand to prime the system and bleed air out of the filters.
A couple mechanics I talked to about 3208's mentioned that it's important that all the hoses and connections from the tank to the IP be good, because a pin-hole leak will allow fuel to leak back to the tank. They also both mentioned using a primer pump to push fuel (rather than sucking) to the IP. That made sense, which is where I came up with the idea of using a low pressure air pump (air mattress inflator) to blow enough pressure into the tank vent line to push fuel up through the system. This worked fine, but I wouldn't suggest using a shop air compressor for this because of the danger of bursting the tank. Remember that 2.5 psi of air pressure is equivalent to 72" of water column, so that's plenty for lifting fuel from the tanks to the engine top of the largest truck.
After growing up on a farm, and working with construction and Ag machinery, I worked for years in the engine room on tugboats and other commercial vessels. a big tug can carry as much as 40,000 gallons of fuel, in as many as ten different tanks. Managing fuel is a big part of an engineer's job, because the fuel can become contaminated with water and bacterial slime. Also because the fuel load effects the vessel's trim and stability. So the engineer keeps moving fuel and water ballast around the boat to keep her riding on an "even keel," and to prevent a half-full tank from making the boat roll dangerously.
One thing that I learned from that experience is that the best way to prevent fuel problems is to regularly "strip" water bottoms from fuel tanks. That usually involves opening a cover on the top of the tank, and sticking a tube down to the lowest corner of the tank, where water settles, and then using a small pump to suck out a little bit of whatever's on the bottom of the tank. On a 5,000 gallon tank you might suck out a gallon or two. On a 100 gallon tank in a fishing boat it might be a cupfull.
Airplanes have drain taps on the bottom of every tank, and part of a pre-flight check is to drain a little bit off the bottom of every tank. My uncle was in the aircraft business, and I still have his special screwdriver for tapping tanks. The handle is a tube made of clear plastic that you drain the fuel into, and then look for water or sediment.
I've worked on boats that have literally thousands of dollars worth of filtering systems, from centrifuges to arrays of Racor water separators. They're very nice, but they don't take the place of sucking water out of the bottom corner of every tank periodically.
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Old 04-30-2008, 10:27 AM   #10 (permalink)
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Interesting comments, Search Engine Optimization.

BTW, I do run a lift pump at the tank on my 3208. It's a hold-over from the previous powerplant, which was a multifuel Hercules DT466. The vehicle is a 1968 M35a2 "deuce and a half".

And, it's been a big year if I run 200 gallons a year through this engine.
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Old 05-01-2008, 09:19 AM   #11 (permalink)
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trango..........jealous......i want a deuce!!
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Old 05-03-2008, 05:54 AM   #12 (permalink)
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Quote:
Originally Posted by Trango View Post

BTW, I do run a lift pump at the tank on my 3208. It's a hold-over from the previous powerplant, which was a multifuel Hercules DT466. The vehicle is a 1968 M35a2 "deuce and a half".

And, it's been a big year if I run 200 gallons a year through this engine.
That lift pump arrangement is exactly what was described to me by some people, who said that if you run the pump for a bit before and just after start-up that it would make sure that the injection pump gets a good prime. That, and making sure there are no pinhole leaks in the lines from tank to engine.

I used to have an old Cat D4 7U, with a big cast aluminum fuel cap that had the advice cast into the top: "Fuy clean fuel. Keep it clean." Words to live by.
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(I usually use my initials, "SEO" as a signiture. Somehow this site translated that to "Search Engine Optimization," which I guess is okay.
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Old 05-03-2008, 12:33 PM   #13 (permalink)
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Yes, this is the case. The solenoid, when energized, retracts. When not energized, a spring loaded dowel pushes down on the fuel stop lever inside the IP.

The mechanic, FYI, could have also used his finger.... that fuel stop lever is accessible through quite a large aperture in the IP top cover, exposed when you remove the solenoid.

Engine was in a rear engine bus. I don't recall how he got the solenoid loose, but he was too short to reach over and push down. It's been a while. He had to work over the running belts......
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Old 05-07-2008, 07:14 AM   #14 (permalink)
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Well, d**n it. I got out to where the truck is yesterday, and checked the solenoid. It's working fine. Even took it off and worked the little shut-off lever up and down a bunch of times. It moves easily.
The only thing that struck me as being strange about the shut-off is that if "down" is "stop," (which it is), when I had the stop solenoid off the lever would move easily, but would stay "down" when the engine was cranked. If I pulled it to "Up" it would stay up, but it wouldn't move itself from down to up.
I hope that makes sense.
My question is this: if the solenoid pushes the stop lever down when the key is turned off, what moves the lever up to "run" when the solenoid is energized and retracts? The solenoid is just a pusher, it doesn't have a finger that engages the lever so it can pull up as well as push down.
Any ideas?
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Old 05-12-2008, 06:28 PM   #15 (permalink)
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Well, d**n it. I got out to where the truck is yesterday, and checked the solenoid. It's working fine. Even took it off and worked the little shut-off lever up and down a bunch of times. It moves easily.
The only thing that struck me as being strange about the shut-off is that if "down" is "stop," (which it is), when I had the stop solenoid off the lever would move easily, but would stay "down" when the engine was cranked. If I pulled it to "Up" it would stay up, but it wouldn't move itself from down to up.
I hope that makes sense.
My question is this: if the solenoid pushes the stop lever down when the key is turned off, what moves the lever up to "run" when the solenoid is energized and retracts? The solenoid is just a pusher, it doesn't have a finger that engages the lever so it can pull up as well as push down.
Any ideas?
SEO

SEO,

Funny auto-replace on your initials.

I sort of stated the answer to your question in a previous post, which I'll restate here, with quite a few edits for clarity:

Inside the IP, there is a wishbone-like mechanism that slides up and down on a chromed rod. With each rotation of the IP works (I think of the IP as a mini-engine-in-reverse, which is what it looks like when you take the cover off), that wishbone gets a little nudge to the "open" position, which allows fuel to flow.

In between this wishbone and the solenoid is the fuel stop lever, which is accessible by removing the solenoid. When the solenoid is not engaged (engine off), the spring in the solenoid pushes the stop lever down, which in turn, keeps this wishbone in the off position.

I'll run through the "Concept of operations" for engine start: Firstly, at rest, the solenoid is unengaged, the fuel stop lever is down, and the wishbone is closed, stopping fuel from flowing. Then, when energizing the solenoid, you will release its push on the fuel stop lever. Since the fueling wishbone mechanism will get nudged open by the motion of the IP when cranking the engine, it will open itself, and in doing so, move the fuel stop lever up.

For all I remember, the wishbone may also be spring loaded. I just can't recall that much detail.

So, if you can't feel that fuel stop lever rise on its own, chances are that you have the exact issue I did. In VERY CLEAN conditions, I'd pull the top plate of your IP, locate that wishbone mechanism in the back/aft part of the IP, cycle it by hand until it moves freely, and then reassemble.

Hope this helps
Bob
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