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fuel shut off solenoid diagnosis

deejaaa

deejaaa

Diesel Beginner
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Location
Texas
93 truck's been sitting 4 years now. it quit on me and figured it was the fuel. removed the IP inlet screen expecting it to be full of poop but it wasn't. jumped the gun and swapped IP and used the same top cover with original solenoids. jumper to start solenoid gets just a spark. remove cover, jumper ground and hot and it will engage. hold it doing the same and it will shock the snot out of me.
is the solenoid bad? was this the reason it stopped on me 4 years ago? new solenoid is 75.00 with shipping. TIA.
 
yep, the 93.
does this sound like a failed solenoid? hate to throw money at a problem.
 
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If I am understanding correctly. It sounds like the solenoid is bad. I never had one shock me before. But then, maybe I was not properly grounded.

The solenoid does have to be grounded to work. If you have the solenoid out and no ground attached, you will be the ground if you touch the right stuff. Sounds to me like maybe what you did.
 
i had a jumper on the ground strap and hot. it shocked me while not touching anything but the cover.
I pulled the solenoid from the cover and it looks fine but guess i will order a replacement.
 
Pull the solenoid & try starting. If it starts, solenoid is bad. To shut off engine, pinch the 1/4" return line (clear tubing one) shut. The stopped fuel flow will kill the engine.
 
deejaaa said:
93 truck's been sitting 4 years now. it quit on me and figured it was the fuel. removed the IP inlet screen expecting it to be full of poop but it wasn't. jumped the gun and swapped IP and used the same top cover with original solenoids. jumper to start solenoid gets just a spark. remove cover, jumper ground and hot and it will engage. hold it doing the same and it will shock the snot out of me.
is the solenoid bad? was this the reason it stopped on me 4 years ago? new solenoid is 75.00 with shipping. TIA.
Click to expand...


What cover are you removing?

Do you have voltage to the fuel shut off solenoid wire with the key turned to run?

You can test for continuity from the connector to ground. I do not think there should be any continuity there.

When the key is turned do you hear the solenoid click as if it was working.

I've had mine out and hooked up, watched them work, never got shocked

A plugged return line will also not let the engine start
 
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I'm removing the too cover on the IP.
I will give all that a check today. thanks. if alls good i will try to start without the solenoid installed.
 
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i have 12.5 volt at solenoid wire with key on. battery reads 12.7.
that's as far as I got today.
 
Does the solenoid click when you turn the key on?

You can run the injection pump return line to a container, Jumper the lift pump and turn the key to on.

You should get a trickle of fuel out the return line
 
solenoid wasn't clicking, just a spark when jumpered.
I have a seperate LP running off the battery when trying to start. solenoid is removed right now. when i get home i wil see if i get fuel out return line when cranking, after i put top cover back on, sans solenoid.
 
jrsavoie said:
Do you have something in the hole the solenoid came out of? With the solenoid out and the lift pump jumpered, you should have big mess of fuel
Click to expand...

Yeah! Good catch on my poor desription.
Dont remove the solenoid, unscrew it a turn or two.put a shop towl to catch the fuel that will come out the threads. Have someone try starting. If it starts: then pinch the return hose or try screwing in the solenoid to kill it.

Did I miss- have you removed the solenoid and supplied power away from the IP to see it working?
 
The solenoid's on a mechanical IP has 2 screw post that has a spade connection to the hot side and other goes to ground. removed will leave 2 holes on cover so i put 2 small bolts through them. they leaked a littler fuel but not bad.
I went through a LOT of cranking and cracked lines but got it started. this is sans solenoid so I killed it per Wills instructions and it shut off.
thanks all for the help. I will get intake on and lines connected. hard parts over.
here it is:
you can barely make out the ATT in there.
thanks again.
 
deejaaa said:
solenoid wasn't clicking, just a spark when jumpered.
I have a seperate LP running off the battery when trying to start. solenoid is removed right now. when i get home i wil see if i get fuel out return line when cranking, after i put top cover back on, sans solenoid.
Click to expand...

The DB2 has 2 solenoids in/under the top cover. When you are testing a DB2 after taking it apart and you test the solenoids and get "solenoid wasn't clicking," STOP!!!

You likely have the metering valve jammed in the full fuel position without a click. The governor is helpless to move the fuel metering valve from full fuel. Hit the starter and you have instant runaway engine requiring a quick action to cut off intake air with a board, etc. Watch fingers and rags that will remove fingers and ruin engine.

I suggest you have a board and a plan to cut off intake air if your engine runs away. Yes, you have to have a place in the intake to do this usually requiring some of the intake removed. For testing the turbo doesn't need to boost the engine so the small intake hole on the upper intake is a good place or drop a board on the lower intake with the upper removed. Practice it a couple times without the engine running and make sure you are clearing moving parts. This way when the engine is screaming you can follow the plan and quickly cut the air off no matter what is making the floor slick and running down your pants. :yuck:

Let me point you to a good article of how it works because they, Ray T. Bohacz, has a good pic of what I am about to describe. A good read, but, How it works is not how to put it together and how to troubleshoot it.
http://www.trucktrend.com/how-to/expert-advice/0809dp-stanadyne-db2-injection-pump/

stanadyne_db2_injection_pump+housing_cover.jpg

Here is a pic of a long ago dead IP of mine:

ip-innards.jpg

Lets start with the big black solenoid in the upper left of the picture. This is the shut off solenoid we care about. (The small solenoid in the lower left top cover is the cold advance.) Lets test it as we have the top cover off.

You already noticed it shocked you. I am not sure if there is a suppression diode built in at all on the solenoid or if it is elsewhere in the harness. My tests were inconclusive this AM. (I now smell like diesel fuel this AM from what leaked out of my surplus pump.) Regardless: Any coil of wire will generate a larger voltage from the magnetic field collapsing. For example the primary side of an ignition coil will generate up to -300V when the points stop the +12v current. If you used a suppression diode you wouldn't get a quick collapse of the field and no 20,000 volt spark on the secondary side. Thus to save the points from sparking/arcing they use a capacitor, aka condenser for the old school folks. The capacitor allows a sudden stop of the current where the diode wouldn't. So for non-ignition coils that are used in solenoids a suppression diode is used esp. for relay coils. The purpose is to save the switches that control them let alone not shock you. Hook the battery up backwards to test and the diode releases it's magic smoke instantly becoming a useless work of art.

So with 12v hooked up the solenoid should move from closed and allow the metering valve to be controlled by the governor. The spring will move it back to full closed with 12v removed. The fuel solenoid is the terminal furthermost toward the front of the engine with the pink wire on it. If it doesn't move at all you have a bad spring, something like debris or rust jamming it, or shorted solenoid windings making a weak magnetic field.

Install of the top cover:
When installing the top cover on the pump you want to offset the cover as far forward on the engine as you can limited by the shut off solenoid tang hitting the engine front inside of the pump housing - the bolts WILL NOT go in! So slide the cover all the way down and them being careful of the gasket slide it backwards till the bolt holes line up. This action brings the solenoid tang in contact with the governor and metering valve control assembly and closes the metering valve that spring tension is holding wide open to obtain 650 RPM from the current 0 RPM. WITHOUT REMOVING PRESSURE ON THE TOP COVER: Run the bolts down. (Otherwise spring tension holding the metering valve closed will pop the top cover up and allow the solenoid tang to jump over the assembly - then you bolt it down locking the metering valve at full fuel.) With all three bolts in apply 12v to the solenoids one at a time. If you don't get clicks "STOP!" DO NOT ATTEMPT TO START THE ENGINE! Figure out why you don't have a clicking sound and fix including re-do of the top cover assembly steps.

The cold advance solenoid is worth mentioning. To prime the fuel system it's faster to have this "off" by disconnecting the temperature switch on the coolant T-Stat crossover. The cold advance increases housing pressure to advance timing - it does this by restricting fuel flow. As we are dealing with air and fuel flow we want flow not compressed air. You start to get white smoke you can hook it back up unless you keep stalling with it hooked up.

When you are ready to start the engine make sure you have a good friend helping crank it or operating the air shut off board. Whoever has the bigger brass balls should be running the air shut off board. SMOKE, runaway engine noise, and legitimate fear of it going "BOOM!" have to be overcome to drop the air shut off effectively and safely as possible. :D

This said the next step is to see if the IP locked up and broke the driveshaft. With a air shut off in place and holding the fuel metering valve closed rotate the engine by hand in it's normal rotation. A diesel can run backwards so let's not give it the option. You are looking down in the pump to see if the governor assembly rotates when the engine is slowly turned by hand.
 
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