It started a few weeks ago when I turned the key on the 1999 Disco1 SD and the truck did not turn over at all. Dash lights come on and I heard relays under the dash clicking. Looked things over and didn’t see anything obvious so tried cranking again and it started right up. Drove it daily with no issues for several more weeks and then had another no start no crank, same as before. However, it’s been several weeks and still can’t get it started.

Thought it was the starter but I’m getting 12 volts at the trigger when turning the ignition and 12 volts on the power terminal. I can force start it by jumping the trigger to the power terminal with a screwdriver. Don’t think it’s the ignition relay since I’m getting 12 volts at the trigger when turning the key to start. Also checked the negative battery thermal to ground and don’t see any issues there.

Thinking it must be an electrical issue but not sure where to start. I’ve read where the immobilizer causes issues with no starts but it allows the engine to turn over but not start, which doesn’t fit what I’m seeing.

Any ideas on what to test next?

Thanks in advanced for any input.

Disco99SD

 

It could still be the starter. They wear out and go slowly. Inside the starter solenoid is a core that if it starts to wear out will allow for it to crank mostly, but sometimes not. But, as time goes on, that core wears down to less and less with the eventuality that it will not start at all. That is a possibility. There have been posts here on the forum where guys talked about their intermittent starter issues and eventually had to replace the starter.

Another issue, and I just dealt with this myself, the wiring to the crankshaft position sensor was burnt out. There are two wires to the sensor. The outside casing had charred away after many years of being so close to heat. The wires were touching and this shorted things out. I heard all of the relays clicking - similar to what you mentioned, but then they would shut down. I replaced the wiring with a new pigtail plugin and now that portion is working.

 

CPS and VSS are failure prone parts due to location and heat on D1's - CPS being responsible for a lot of no starts

Starter can wear and cause intermittent issues and a poor ground connection can cause no start - also double check the battery terminals are clean and on tight which can cause this too

 

Update - cleaned the battery terminals which didn’t help so I ordered a new starter and CPS. Already took the old starter out and new one should arrive tomorrow.
Question on the CPS - when it goes bad does the engine still crank?

Will keep you posted.

 

yes. The engine will turn over but, without the CPS working, the engine does not, in effect, tell the fuel nor spark to work. You can test this by testing for spark and on the fuel rail there is a Shrader bike valve. If you unscrew that and depress the post sticking up this will release the fuel. Then test again. If you have no spark while also have no fuel pressure in the fuel rail, then the engine computer does not know that the engine is turning over, the function of the CPS. But, the alarm and the ignition can fault these things as well.

 

Replaced the starter and still have no crank issue. I can start the truck by shorting trigger to 12v supply on the starter. I think the ignition is ok, I get 12v at the trigger terminal when I try to start with the key.

Next I will replace the CPS, stay tuned.

 

Maybe get a wiring diagram and work through the starter control circuit. If it starts by jumping the starter solenoid, then the CPS is fine and everything else is OK.

 

Do you have fuel in the fuel rail? And, do you have spark? Before you yank out the CPS, check for spark & fuel in the fuel rail. Also, and sometimes this is an issue, check the fuel cutoff switch on the firewall on the passenger side. All you have to do is depress the top and it is reset if it had been triggered. I had an issue one time, and this thing somehow was unplugged. I was not getting fuel to the fuel rail although I had spark. Trust me when I say I lost hair from pulling it all out of my head chasing that issue down. The clip was old and broken and simply fell out. It is zipped tied together now.

But, definitely check for fuel in the fuel rail and that there is sufficient pressure. You can remove the shraeder valve and depress the little pin inside. Fuel should squirt out - be cautious of this. Let a lot out. Then, try starting again. Fuel should refill inside the rail again. If it does, then you know that this function is working. But, if you also have spark you will know that the CPS is functioning properly simply because you would not get any spark if the CPS does not detect the crank shaft moving.