Hey guys, I am new here and have a few questions I am hoping you might be able to help me with. I am on a small volunteer fire department and we do not have much money and our 1992 ford 7.3L ambulance is having some problems. We have taken it in a couple times and no one can seem to fix our problems. As a back ground we have had the alternator, fuel filter and batteries replaced recently trying to fix our problems.

Problem #1:
Sometimes the ambulance is hard to start. It is also pluged in, but I do not think it is a block heater just a shore line to charge the batteries because of all the lights and electrical equipment we run. But it is atleast 60 degrees in our bay so I do not think a engine block heater is needed. It will crank and crank but nothing. I have tried cycling the glow plugs a few times and it still doesn't help. Other times it starts right up.

Problems #2:
When it is running it charges fine, but when we turn all the emergency lights on and it is idling the voltage will drop down to 9-11. We do have a high idle switch that we turn on when idling with lights on, but it doesn't kick it up very high. It will charge fine if we give it a little gas and the voltage will go back up to 13-14. I think the high idle should be higher, but I do not think the voltage should drop to 9 right away. I undertstand if we ran the light for an hour without the high idle that the voltage mwill drop.

Any help is greatly appreciated because I know gas engines inside and out, but do not know a great deal about diesels.

thanks
Tom

 

for the hard start problem, look to see if the fuel filter has a line going to the injector below it. if it does, block it off, and the hard start should go away.
as for the low volts at idle, you can either go to a higher amperage alternator, or try to turn up the high idle cam

 

you may still need a bigger alt all them lights draw alot of amps
or mite be able to go to a smaller pully on it
are you running a 200 amp alt or bigger ?? if not you need one
a stock 120 or 140 amp hd alt wont keep up with the lights
Back in the day when i was on a fire dept our ford amb-rescure rig
had a custom built 225 amp on it & it would barely keep up at idle
everything else had 300 amp or bigger on them
it also sounds like you said needs a higher idle
if i remenber right it took ours 1100 to 1300 rpms to keep everything powered up
just a thought give a 4-5 sec delay between flipping each switch on for the lights
cause the strobes have to charge up the caps before they flash

ok motor heads speak up im not the 7.3 expert lol
hope this helps

 

Welcome to FTE.

You can also have the starter checked. It might be slowing down. Don't crank it for more than 30 seconds without letting it cool a bit.

You need at least 200 amps.

The plug for the batteries is different than the block heater. You should have a heater. I can't imagine them building it without one. Contact the company that built the body and ask them about it.

Have you tested the glow plugs and controller? Is the fuel filter clean? If the fuel pump good?

 

I would suspect the glow plugs are to blame for the hard start.
How long does the wait to start light stay on?
If it is less than 10 to 12 seconds you have a couple of bad glow plugs.

 

My 7.3 IDI stater was slowing down, making starting hard, was due to worn starter brushes, causing weak contact between brushes and commutator, ie poor current flow. a new set of brushes and cleaned up commutor brought starting back up to normal

 

When you say nothing do you mean - no smoke, sputtering, anything.When you have this problem do you hear a clicking noise from under the hood? If not. Might be the glow plug controler is starting to go bad i've replaced mine 3 times in 12 years. I sounds just like the problems I had. The controler is located behind the air cleaner under a plastic cover. Real pain to get to unless you can sit on a motor.

 

Pull the doghouse on an E series and the controller should be right on top in front of you.

 

Thanks everyone for all the help. When it doesn't want to start it turns over but will not fire. Sometimes it cranks slow but I think that has to do with the charging problem. Others it cranks just fine but won't fire.

I have thought all along that the high idle needed to be turned up, but how do I do that?

How do I test the glow plugs controller?

How can I tell what amp alternator it has? Just use a meter?

thanks
Tom

 

for the hard starting problem, you may be suffering from dried out o rings beneath the fuel return caps and the fuel is draining back. the light problem, you may be suffering from old batteries and they should be changed as a pair with all connections and cables replaced and really clean. the block heater should be standard equipment with the plug being hidden along the bumper.

 

Hey guys. I found out tonight that the batteries and the fuel pump have been replaced in the last 2 months. I think the whole fuel system was just checked because we were getting air in the fuel lines. I will have to get the work order and see exactly what was done.

I was wondering how I would up the high idle? It really needs to go up about 300-400 rpm at least. When turned on it only goes up about 100rpm. Is there away to adjust that? Because if the lights are running and I give it a little gas it charges just fine. I think this will help with some, but not all of our problems.

thanks
Tom