Gauge issues?

[brownbear]

Hey Guys,
I have a 91 7.3 idi in my E350 motorhome.

Last summer I had it overheat on the gauge pegged all the way to the top, twice or 3 times while trying to reach a city. It never boiled over or appeared to actually happen, other than the indication.

I had Ford check it out and they changed the thermostat and maybe even had them check the gauge for proper indication.

I drove for about an hour up and down in the mountains, then while going thru a city at light load it went up really high in temp. At this point I think I noticed the oil pressure also go up and fuel indication went down...?

Anyhow I decided to ignore this and continued driving 800 miles home through the mountains of BC. I had a couple slightly warmer times on the temp gauge, but nothing pegged..

After being parked for a couple weeks I hopped in and my fuel tank of fuel showed empty, well actually about an 1/8 remaining with a confirmed full tank.

Does this sound like purely coincidence? Is there a common ground issue in these instrument clusters?

I'm not sure quite where to start.

Are there any good write up's on what I need to run an aftermarket water temp gauge and where to put the sensor etc? Like what is exactly needed to order?

Also this summer I need to have a transmission shop put in a shift kit and torque converter, what is the best one for heavy motorhome? I have slippage under heavy load on hills when it is hot. I already put in the power module for the transmission.

If anyone know of a good kit for aftermarket gauges with water, oil px etc please let me know.

Sorry for all the questions.

 

[The Warden]

The gauges on these trucks are iffy at best. I would strongly recommend installing aftermarket water temp and oil pressure gauges and see what sort of numbers you're really running, particularly on something with the weight and sail area of a motorhome (and, a pyrometer would also be a really good idea even on an n/a engine). As to where to put the sensors...if the stock gauges functioning isn't important to you, it would be simplest to replace the stock sending units with the aftermarket ones. The stock oil pressure sender's on the back of the engine block...in a van, if you pull the doghouse cover, it should be pretty much right there. The water temp sender IIRC is on the driver's side cylinder head, forward, near the injector pump gear cover. There are two sensors on the driver's side cylinder head; one's for the temp gauge and the other's for the "Overheat" idiot light. There's a similar sensor on the passenger's side cylinder head; this controls the solenoids on the IP for the cold high idle and cold injection timing advance.

With that said, if you have a stock '91 cluster on your van, that should have the same instrument voltage regulator (IVR) on the back that the '80-'86 F-series trucks had...and, yes, that voltage regulator's a trouble spot. If you're noticing that the water temp and oil pressure gauges are moving towards the top together, particularly if it's happening when the cab's hot (either on a hot day without a/c or with the heater going full-bore), that's a classic symptom of IVR problems.

IIRC the IVR also has something to do with the fuel level gauge, but you could also have had a sending unit go south.

Hope this helps...good luck, and welcome aboard

 

[brownbear]

thanks very much about the IVR information. I never heard about one of those before. I will try replacing that.
I would not mind keeping both aftermarket and stock gauges working.
I put a PYRO in a NA Toyota diesel and it was quite the eye opener. I would imagine my 12,000 lbs motorhome is going to pushing those temps up pretty high!

What is the typical oil pressure, water temp, pyro temp, these trucks run at?

Thanks,
BB

 

[The Warden]

I didn't know how feasible it was to replace the IVR...but, I just did a Google search and found this thread:

http://www.ford-trucks.com/forums/877622-instrument-voltage-regulator.html

Maybe that'll help you? Honestly, I abandoned the factory gauges on my truck...except for the fuel level gauge (which, amazingly enough, works on both tanks) and the speedo, my instrument cluster's just along for the ride

Re: gauge readings...the thermostat opens at 192 F, and you'll generally see water temp readings in that area. Personally, I wouldn't want my water temp getting above 210 F or so, but IIRC you're reasonably safe up to 230 F. Unfortunately, the "overheat" idiot light is supposed to kick on at 244 F and, by that point, it's too late. Oil pressure...at freeway speeds, expect to see about 40 psi...at idle, you'll likely see 10 psi or 15 psi if you're lucky. As to the pyro...there's really no one-size-fits-all answer. Dependent factors are how heavy the rig is, what your rear end gears are, what turbo system you have (or if you're naturally aspirated). You should get the probe as close to the cylinders as possible...ideally in the exhaust manifold. Aluminium starts to melt at 1250 F, so you really want to keep the temp below 1200 F or so to keep from damaging the pistons (the weak spot in the combustion chamber)...

 

[brownbear]

I didn't know how feasible it was to replace the IVR...but, I just did a Google search and found this thread:

http://www.ford-trucks.com/forums/877622-instrument-voltage-regulator.html

Maybe that'll help you? Honestly, I abandoned the factory gauges on my truck...except for the fuel level gauge (which, amazingly enough, works on both tanks) and the speedo, my instrument cluster's just along for the ride

Re: gauge readings...the thermostat opens at 192 F, and you'll generally see water temp readings in that area. Personally, I wouldn't want my water temp getting above 210 F or so, but IIRC you're reasonably safe up to 230 F. Unfortunately, the "overheat" idiot light is supposed to kick on at 244 F and, by that point, it's too late. Oil pressure...at freeway speeds, expect to see about 40 psi...at idle, you'll likely see 10 psi or 15 psi if you're lucky. As to the pyro...there's really no one-size-fits-all answer. Dependent factors are how heavy the rig is, what your rear end gears are, what turbo system you have (or if you're naturally aspirated). You should get the probe as close to the cylinders as possible...ideally in the exhaust manifold. Aluminium starts to melt at 1250 F, so you really want to keep the temp below 1200 F or so to keep from damaging the pistons (the weak spot in the combustion chamber)...

thanks for the info!