I have a head scratcher here. Ingersoll air compressor with Ingersoll Rand brand diesel engine (made by Isuzu not Yanmar). It will start and run as long as you hold the key on start. I tried a new key, relay, and then started checking every wire. Turns out I do not get 14.7 volts from the alternator...it does not output anything just shows battery voltage. So I decided to put a jump wire on relay pin that is fed by the alternator (hoping that would fool the relay into keeping the fuel shut off solenoid on when I let go of the key and let it go from start to run) but the fuel shut off solenoid closes right back up the second you let off the key from start to run. If I bypass the fuel shutoff solenoid the machine works beautiful EXCEPT of course the alternator is not charging. So I have a replacement alternator coming - however I am unsure if that will help me figure out when the fuel shutoff solenoid won't stay on once it starts. Its the only thing I can tell would get power to the relay after the key is switched to run. Any ideas?
Is there 12v on the red wire (in run) at the stop solenoid?
Yes but only if you hold the key on start which is bringing juice in from the key. On run there is no 12V at that same relay from the key and I BELIVE but I am not sure that the 12V is to then come from the alternator? I need to reread that electrical diagram and maybe a little closer. Would a picture of the diagram help you determine where the juice is to come in after start voltage is removed from the relay (this same relay is where the fuel shutoff solenoid is wired in)?
I'm used to 3 wire stop solenoids. Black...ground White...pull in Red...maintain On or two aftermarket ones for my Yanmars had to be repinned as the white was the maintain. How many wires on yours? And, yes, a schematic would help immensely.
I am used to the 3 wire myself. This is factory 2 wire per the diagram and that is what it has. Solenoid works fine but I am not getting juice to it once I let go of the key. I am wondering if from the diagram you can tell which of the other power sources could be neglecting to send power. There are 3 gray and gray striped wires that all come to the solenoid and then the 1 solenoid positive wire connects to 3 gray wires. I have a new alternator coming but I don't know if that would change anything here (there is that VIO/YEL wire that goes from relay to alternator and that relay also sends power to the fuel solenoid from Gray/Black). Gray/blue is sending power TO the hour meter right? Gray solid connects to oil pressure switch but if I touch those wires together it still doesn't change a thing and the fuel solenoid switches off the second I turn from start to run.
Grab a test light check power at engine temp sensor and oil pressure sensor could have bad sensor
Turn the key to run. Is there 12v at (1)? Testing at (1) eliminates 2 switches (3 if it has the low fuel shutdown). Is there 12v at (2) (pk w/bu)? No sense in testing the other side (lt bu/rd). Your answers will tell us where to bypass. Reading the schematic, there are no relays involved in staying running, nor is the alternator involved.
Have you checked oil pressure, engine temp and compressor temp switches (or the wiring to them)?
Thanks folks! I have power at 1. I do not have power at 2 (either of the oil pressure wires). Now this is with the key ON and engine not running. Is RED/BLK ultimately the power source to the oil switch? I do not see a low fuel shutdown as it doesn't even have a fuel gauge.
Then check the engine temp switch. Yes
With key on there is supposed to be 1 hot at the temp switch right? And if not I go back to the compressor temp switch and again with key on there should be 12V right?
If you have voltage to #1 (Bypass Relay) pin 30, then you only need to go back as far as the engine temperature switch. If it starts and runs while holding the ignition in start then there should be voltage to pin 30 of that relay.
Sorry now I am messing up the process - I checked just now with the key on (not start) and there is NO voltage at 30 on bypass relay. So we are not getting juice on RUN position to 30 on bypass relay. EDIT: should I be chasing back YEL/BLU wire that goes to bypass relay?
No. Yellow/Blue (Pin 85) should only have voltage when cranking. Pin 30 should have voltage any time the ignition is on.
Thanks. I will pull the wire that goes to 30 out of the loom and chase back to the key but it might make sense to run a new wire from run to pin 30 on relay.
You need to find out why pin 30 has no voltage. So you have to back track on the schematic from there. Jumping voltage to pin 30 will not keep the unit running when you stop holding it in the crank position. That relay is only for bypassing the shut down system until you achieve engine oil pressure.
Thank you so much. Ill take pin 30 back like you say. Theres a jumper in there to bypass the low fuel shutdown but I'll still check both sides as I work back to RED/BLK. Will post what it was as soon as I have it!
With key on I have voltage at one side of both the thermal sensor (TS1) and compressor temp switch. The wire that is bringing juice into each of these sensors and have voltage is PNK/VIO. Are either of those sensors supposed to always provide 12V unless there is an overheat situation?
EDIT: it was the temp sensor! Jumping the sensor got her going. New one will be here tomorrow! Thanks all!
Parts... Thanks for coming back to share the solution. It grinds my gears when someone gets suggestions and then ghosts the forum. It's a disservice to future searchers and rude to the forum members that tried to help.
Totally agree with you. I love getting and giving help...I don't love giving help and the mystery of the repair remaining unsolved in my mind . What would have really helped in this case was being a better electrical diagram reader. I need to find a book and read read read until I am as good as you guys.
What kind of juice are you looking for? Grape, orange, apple? Bob
Definitely not grape! But pineapple works
Trying out the brain trust again on this one before I do any further digging...got the same machine in again (different machine but same engine and wiring diagram). This one will not crank until I unplug the gray wires that go to the fuel shutoff solenoid. Just to do some diagnostics I checked every sensor and 1 side is hot with the key on. I made a jumper wire for each of the engine and air end sensors (except the water temp sensor as I did not have the correct wire ends - and perhaps the issue is with that sensor) and still no start. Not sure if one of the sensors should be able to prevent starting or why unplugging the solenoid would allow the starter to crank. Any input appreciated - will be in the shop on this one tomorrow. Thanks all.
Really scratching my head here. If I by pass wire the oil pressure, water temp, and 2 air end sensors then what else is left? I don't believe there is a low fuel shutdown on this machine because there isn't anything going to the tank. I definitely have 12V going to both sides of each switch that I bypassed (with key on that is). Like I said above it will crank just fine if you unplug the gray wires at the fuel shutoff. Both relays tested fine. Could that glow plug timer do anything to hurt starting? The oil pressure switch is coated in oil so I am sure it needs replacement but I have it bypassed anyway at the moment.
CHeck grounds. Seems from the diagram, the grey wire supplies power. With power there's no voltage difference, disconnected, power flows backwards.... And the relay closes & cranks.
Thanks. Gray is power for sure. So can you help me understand a little better. When I unplug gray (and manually hold fuel lever) it will crank and run. So I am guessing gray isn't getting power right? I will check with volt meter tomorrow but if it was getting power the solenoid would move (solenoid is working fine when connected to battery). Now you're saying gray is not getting power because of a bad ground so ill add a clean strap and clean current ones. But what is gray grounding that won't allow any cranking unless I disconnect gray?
No.. I'm saying gray is applying power ... If two wires are both connected to + 12 volts .. the net voltage is zero across a coil. When you take away the grey, then the net voltage is 12 volts through the loads grey is supposed to energize. And some relay coil energizes.
Gotcha - makes sense. I'll clean the grounds but maybe add a block to frame/battery ground to ensure everything attached to the block is grounding. Will report back.
Any update on this i seemed to have been blessed with the same model doing the same thing?
machine was in for repair. Customer complained unit would not stay running without them holding the fuel shut off lever open. Found discharge temp switch bad, and the starter protect relay burned up. replaced both. unit started and ran however alt was not charging replaced alt and battery. two months later machine returns, found the fuel solenoid burned up, and also the same relay cooked again. replaced those, try to start and no go fuel sol will not stay energized long enough to run, i jumped out water temp switch and thermal sensor on sep tank and still no go