cold start issues 4d55

My unit is a new to me 4d55 swapped into a former gas '91 Isuzu pickup. Will not start in the morning without plugging in the block heater. Fires right up if I do. Temperatures here are 40 degrees and less this time of year. I have worked thru many issues successfully, but this one has me stumped. I have 400 lbs compression each cylinder, am getting fuel, have a manual glow plug switch (Ford type solenoid) using new 12 volt NGK glow plugs. It does not seem to matter how long I run the glow plugs (and yes there is power to them) it will not fire. I'm afraid of a really cold day chilling off the motor and being stuck somewhere without a plug-in for the block heater. Any suggestions anyone?

That is one of the downsides to these engines, diesels like these don't really start to run right until you get them up to temperature. If you don't plug it in one thing you can do is just try to start it like normal, hit the glow plugs and go for it, it will probably take a good bit of turning over before it gets going. After that let it sit and idle for a while, maybe put it in neutral and rev it up a bit, it should start to sound like normal after a little bit. Just don't immediately cold start it and then try to drive it, that can be really hard on any diesel.

The mitsubishis use 6V glowplugs with a big resistor to take up half of that voltage. The reason is that they can put a full 12v over the glowplugs for a couple seconds to heat them up really fast, and then the solenoid switches over to put the resistor into the circuit, so that the glow plugs don't burn out.

I would think that your 12V plugs should be fine, provided you aren't putting that resistor into the circuit... They'll just take a few more seconds to heat up than the original mitsubishi design.

So the other question is: how vigorously does the starter turn the engine? Maybe a more burly starter and or battery can help? Maybe a lighter weight oil?

Or, you can carry some briquettes and start a fire on the ground, then roll the truck over the coals when they've died down a little bit. Maybe a metal lid over the coals so you don't set the thing on fire. This is just an idea that popped into my head.

I know that with my 12V set up if I push my manual switch for more than 6 seconds they burn up and then don't work at all and my only choice is to plug in the truck followed by a new set of plugs. I usually push mine for 4 seconds let it turn over with the throttle knob open all the way and then will stop and push the switch for another 4 seconds and then it fires right up. People in parking lots usually will look at me wondering if my truck will start.

I had a friend years ago that used to start a fire under his old chevy van to start it in the winter-don't know if he ever burnt it to the ground though...

When I was working in Wyoming in the gas fields and we weren't near any electrical plugs to plug in the block heater we would just stick a couple of those forced air kerosene heaters towards the block and the batteries for 45 minutes and then usually the big rigs would fire up. We'd do the same for trac-hoes and dozers too. When you'd smell rubber or plastic burning that usually meant something was getting a little hot.

You most likely burned them up already. If you run 12v more than 8 seconds they will be toast

Actually, the originals were not burned up, even though they were wired to run with the starter, which must have been run a lot to get this thing to start not plugged in. The new one's are the 12 volt NGK's and it is my understanding that they can handle a full 12 volts for sometime without issue, compared to the originals on the step-down relay.

Hmmm? The only other advice I'd have for you if they aren't burned up is to just make sure that everything is connected up really clean and make sure there's isn't a short that has melted somewhere along the way. My battery is under the bed behind the cab and I had to get 8 feet of new copper wire connected to my relay and starter when I first got the truck. Made a world of difference. I also know that the glow plugs can also burn up / break down internally and not look on the surface to have anything wrong. Test them with a volt meter to see how much is still passing through. If there is a significant reduction in voltage passing through then there is probably some issues internally.

If I remember there was a thread with part numbers that will convert them to the 12 volt ones

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Originally Posted by camoit

If I remember there was a thread with part numbers that will convert them to the 12 volt ones

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http://www.mightyram50.net/vbulletin...g-replacements!

I still think my question asking how vigorously the starter is turning is worth exploring. If it is slow due to a cold battery not producing enough current, in addition to cold oil being too viscous, then you have two possible avenues to remedy.

Turns out the issue was the electric fuel pump. Somewhere pressure must be lost during the time the motor is shut-off. When starting, if I turn the fuel pump on with the manual switch and let it run for 20 or 30 seconds, turn on the glow plugs with their manual switch for 10 seconds and then crank the starter, she fires right up!

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Originally Posted by r.anger

Turns out the issue was the electric fuel pump. Somewhere pressure must be lost during the time the motor is shut-off. When starting, if I turn the fuel pump on with the manual switch and let it run for 20 or 30 seconds, turn on the glow plugs with their manual switch for 10 seconds and then crank the starter, she fires right up!

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Glad to hear it is solved! I'm pretty sure that on the Mitsubishis, there is no electric fuel pump (or lift pump as people seem to call it). Fuel is just sucked all the way from the tank, through the filter (which has a priming pump), simply by the Injection pump. It makes me wonder if your electric pump is even needed?



Speaking of the priming pump (the hand pump on the filter head), does anyone have a recommendation for replacing or repairing it? Mine seems so leak a generous amount of fuel whenever I try to prime it.