Injection Pump Fuel Flow Question
 

I've been trying to find a way to simplify my fuel shut-off system on the S-10. As I looked at the fuel supply system it caused me to wonder:

1) If I put a solenoid valve right after the pre-filter (which in my case is about 5" from the underhood fuel tank) would that cause an engine shut down?

OR......

2) Would the fuel filter cycle it's contents until empty, delaying the shut down until the filter is drained?

3) If I did something along that line would I just NOT put vacuum to the IP shut-off system?

Input!! I need INPUT!!!!

And thanks -

Dan

You will be dead heading the input of the lift pump. First, I don't think the lift pump will like it. My guess is it won't shut off immediately. Easy enough to try it. Please shoot a video and post.

This would be really bad for the IP as the elements are lubricated by fuel. As such you'd basically be starving it of lubrication everytime you shut it off.

If your looking for something really simple maybe go for something like the old front end loaders used. You would lift up on the accelerator with your toe, which would pull instead of push on the linkage and it would pull the IP into the off position. I think it was actually called a deaccelerator.

What I need to have happen is this:

If there's an accident the first thing the safety crew will do is switch off the main power switch at the rear of the car (a battery kill switch is required and I do have it). At that time the engine must be simultaneously killed. Any Diesel will take a few seconds to shut down which is the best that can be done and I think the safety folks OK with that.

What I have is complex but hopefully (needs to be tested) will activate vacuum from a reserviour to effect shut-down using the factory vacuum diaphragm system. I was just trying to come up with a simpler way.

My confusion lies in the internal fuel routing in the IP. Maybe another way to phrase the question is:

When the factory shut-down system is actuated, what happens inside the pump? Does it block fuel flow out of the pump to the injector lines, does it stop fuel flow into the pump, or???

Can anyone post a good functional cutaway drawing on the pump showing what the shutoff system does? If I could see that it might give other possible solutions. Maybe I could replace the vacuum can with a linear motor (solenoid similar to what they use for a power door lock) making for a simpler system.

Again, THANKS all!

Dan

Google Bosch MW pump PDF

Do you have a stop lever on your pump. If so the most direct way is a cable that attaches to it.

Try this thread to understand the operation.

http://www.peachparts.com/shopforum/diesel-discussion/355473-how-does-w123-shutoff-system-work.html

Too easy a present system to bypass. Even a cheap mityvac would allow you to build enough vacuum to shut down. Or a tiny electric vacuum pump motor/pump as the shutoff does not consume vacuum.

You would only activate it when wanting to shut down. I have heard of some people just sucking on the vacuum line extended into the reach of the driver.

Mechanically putting the lever on the injection pump into shutoff mode is another way that would work well. Either by cable or electric solenoid.

When the vacuum actuator is activated it pulls on the rack, moving the elements into the stop position where they pump no fuel, thus cutting off flow to the injectors and stopping engine

Again, THANKS all! I'll go peruse those links here in a minute.

Those who are offering various mechanical or driver-applied vacuum scenarios - I clearly haven't communicated the issue well. The safety guys have to be able to walk up to the back of the truck and flip the battery (main power) switch and have that result in an engine shutdown. If the driver is incapacitated any driver-applied solution no longer applies. Anything less than that isn't safe and won't pass the tech inspection. One possible solution would be a solenoid that would press the linkage shut-off lever whenever power is removed but I suspect there's too much room for system failure to pass tech - but maybe not. It IS a possibility.

Here's a pic of the main power switch, just to be sure we're all on the same page. Nope - it won't let me repost the pic as it's already in my build thread (wish they'd change that). Basically, it's a battery main power switch mounted in the right rear corner of the truck.

Dan

The only option that I see here, that is even remotely simple would be a power close solenoid, which is I think what you are describing you have. So that with power on it closes, no vacuum to shut off, but if the main switch was flipped it would open and apply vacuum to the shut off

Another option I suppose would be some sort of flap that clamps off the air supply to the engine. If you could find an actuator that pulled against a spring it could work. Power on, the actuator opens the air flap, power off the spring slams it shut.

That's kind of what I'm thinking about, only to apply the manual shutoff lever on the linkage.

Much to think about........

Dan

If can find a SPDT vacuum solenoid switch that can vent the common port when electrical power is applied to the coil and connect vacuum to the common with no power, you could connect that to the IP shut-off valve. Vehicles in the 1980-90's used many vacuum solenoids for emissions when they had kludged carburetors. At least I have seen many Chryslers like that when in the junkyard.

Your plan to cut-off the lift pump inlet sounds possible. The suggestion that it could damage the IP by letting it run in air sounds silly. You are not letting in air, just reducing the inlet pressure. Similarly, you might bypass the mechanical lift pump and use an electric pump. There are many on ebay. I recall one for $35 says for gas or diesel, and I suspect all gas ones would survive fine in diesel.

Thanks, Bill. I have the solenoid you describe that I ordered from Peter Paul and that's what's in the current system, with vacuum from a VW electric pump. I was just think out ways to simplify the whole deal - I have to explain it to the tech inspectors so it has to be understandable. What I have makes sense to me but might not be so easy to describe to to someone not familiar with the M-B fuel system.

I think that once the engine is running I'll try pinching off the inlet line and see what happens - that's free. The worst thing would be that it circulates the filter contents thru the pump so the engine won't shut off. If that works, a simple solenoid valve or motorized ball valve and we're home free.

More R&D.

Dan

By deadheading the inlet of the lift pump will not damage the IP from lack of lubrication but may displace the o-ring = "piston ring" of the lift pump. It would be cool to see a video of a test.

It is easy to test what would happen if you cut the Fuel Off before the Plastic Filter. Simply Clamp off the Hose/Line and see how long it takes to shut off.

If you do that the Elements are not going to be dry as there is till Fuel inside of the Fuel Injection Pump Housing and the feed hole on the Element Barrel is under the highest level of the Fuel.

Also a lot of Fuel Injection Pumps use an Electric Solenoid to cut off the Fuel. All of the older VW Rabbits and the same with My Volvo Diesel.

There is no O-ring on the Fuel Supply/Lift Pump Piston. It is a metal to meatal slip fit.