Does sd25 really run with no electricity?

[Daniel]

My '85 720 sd25 wouldn't start the other day although I have been driving it daily for months. I tried boosting it but it still didn't turn over (just made a clicking sound). So I started it by pulling it behind a friends truck and it seemed to run fine. I made it 20 km down the hwy and the engine started to die again, but the funny thing is that the battery died with it, so much so that I couldn't run the radio or lights. Did my engine die because I had no electrical power? Once I get the engine started should it run indefinitely on fuel alone? or is there some peice of the system that needs electrical? I wish I knew.

[philip]

Your answer {Does sd25 really run with no electricity?} is "Yes" and "No".

Consider:

1) Your battery, your starter solenoid and/or wire, your starter, and the DPC module (positions the injection lever) must all be good to start. We have posted a LOT about the DPC matters recently. And your glow plugs must work correctly when the engine is cold (<110 F degrees).

2) Purely speaking, the engine does not require electrics to run until the fuel runs out. Except ... when the DPC (electrically) overrides fuel ... which it is supposed to.

Now I see you are Canada which makes a small difference about your fuel injection system. We USA and many others have the Bosch Inline injection but you may have the Bosch VE rotary injection. In the VE, there is an electrical solenoid that turns OFF/ON your fuel delivery located on top of the Bosch VE. The VE's solenoid turns open fuel when electric and turns closed when electric dies.

So, why is your battery running flat?

[asavage]

Welcome, Daniel, and Thanks for putting your location in your profile.

To state what Philip said differently: the SD engine with the Inline IP will, once started, run fine without electricity. If the system is "stock", the DPC controller moves the fuelling lever from the Stop position to either the Start or Run position. With no electricity, it won't do that, so the IP fuel lever remains in Stop and no matter how much you tow it, it won't start.

The SD engine with the VE Distributor IP is completely different. It has a fuel stop solenoid which must be powered to allow fuel flow. You don't need very much power, but some is definitely required to run this IP.

The Inline IP:



The VE Distributor IP:

Did my engine die because I had no electrical power?

Likely, yes.

My guess at this point is that your charging system is not working, plus you tried boosting your battery with the usual non-diesel battery cables (typically 4 gauge wire, useless for starting a diesel). If you have to jump-start your truck again using those cables, connect them up and run the other vehicle at a fast idle for several minutes minimum: the other vehicle's charging system can charge your battery via the booster cables, greatly reducing the load that the cables have to carry when you try to start your rig.

[Daniel]

Thanks for the replies. I replaced my alternator (after reading a lot about vacuum pumps of course) and I'll have to wait until morning to get it charged and tested. I'll let you know what happens. I think you're absolutely right about mine being the bosch VE type. Thanks again, I'm overwhelmed with the help.