oil pressure gauge problem

[RuralRoute C-30]

(Originally posted in the wrong forum)

So the '85' C-30 got front and rear seals replaced along with the oil pan gasket and timing chain(old one was loose) and cover, and now, the oil gauge reads as if the motor was on when its not. Even when the ignition is on it doesn't move. Coincidence or maybe a bad sending unit appeared? Was a ground I didn't notice get touched in the process?

No leaks around the sending unit.

Is there a way to test to see if it is the gauge or the sending unit? Dare I ground the wire from the sending unit and expect what, if anything to change? It is a one wire sending unit.

Beats me how one fix leads to another, and nothing near the sending unit was touched, but hey, it is an old truck and I am an old man which makes me quite familar with getting fixed in time for something else to break down!

Any suggestions is appreciated as "I do not know", bad sending unit, ground, gauge?.
Thanks,
Mark

[Restrorob]

Go ahead and ground the sending unit wire, The gauge should peg to the highest pressure when the key is turned on. If it does replace the sending unit. If it doesn't check fuses first then for power to the gauge, If you have power to the gauge check for continuity in the sending unit wire from the unit to the gauge. Could be a broken internal wire.

[RuralRoute C-30]

Thanks! What you said makes perfect sense. Now if I can apply it in the morning to isolate the problem.

Seriously, it helps a lot and glad to have a plan tomorrow on this topic. Just having to return to thinking mechanically after a few years away from 'old iron'.

It reminds me I have gotta buy that repair manual soon!

Appreciate the knowledge always,
Mark

[TheSleeper]

i had similiar issue and i finally took the gauge out, laid it on the battery, ran a hot and ground jumper, and then a jumper to sending unit, started truck, and found that the gauge and sending unit worked fine. sorta easy test for the sender and gauge if you have gauge out anyway. unfortunately i cant remember which posts were which off top of my head, i had a little diagram, which of course i probably tossed in the trash.

in my case, somehow i lost power to that socket only in the dashboard, as well as sending unit socket for oil pressure. i had to jumper a hot wire from the key on hot of my temp gauge below it, ground it, and run a new wire from sender to the other post on the gauge. I put it back in stock location and the oil pressure gauge has worked ever since.

[RuralRoute C-30]

Thanks for that advice. I did go out to my shop last night (beats watching television when I have a task on my mind) and discovered the fuses are all good and the wire to the switch has power when the key is on. Gauge is pegged to where it ordinarily would read at this time with no key on.

Plan to go to the local parts house this morning for the sender to go that route first.

Doing my best to not complicate the simple. A learning curve for me as that is one thing I am good at. Just getting to "know" this new "old" truck!

Always appreciate learning from those who "have been there, done that'.

Obviously I have bought into another "hobby"!

Mark

[RuralRoute C-30]

Well the trip to Autozone was educational. Apparently the oil sender this truck came with is for a 'light'. The 'gauge' sender, $19.99 at Autozone) will require some plumbing for clearance from the distributor.
Old vs. New:


Now remember, this is a 'new' used truck that already I've confirmed is not with the original motor. Yet I still recall looking at the gauge when I bought it and I swear the gauge moved...? Oh well, at this time I just want to make it right even if I am wrong and have an oem electrical oil gauge working. So should I just plan on plumbing what is supposed to be the correct oil sender for a 'gauge' and then see what happens? (parts stores didn't carry the plumbing parts but there is no way that gauge sender will fit without being raised a couple of inches and relocation away from the distributor)

I did go ahead and install a new $7 sender, the same as the one I pulled out, just to try it. Nothing changed.

Here it gets interesting as I decided to go ahead and pull the gauge cluster. Only two lights were working anyway and why not take a look at behind the gauges? This day was already going 'south'!

The pics tell the story of what I discovered:
Any input is welcome. Looks like one project has led into another and so it goes. Yet it is better to do this now than when I need this truck. Also this truck was known to have sat for at least 12 months until the guy I bought it from bought it from the original owner last August. (I've had it for a month)

I do notice a lot of corrosion behind the oil gauge as seen in the pictures.






Since I have gone this far I want to focus on both getting the oil gauge working properly as well as what is needed to clean this mess up. No point not to imo.

Question: Is the back half of this gauge cluster worth cleaning up with the corrosion around where the oil gauge is? Is it compromised with so much corrosion?

Any advice to clean this mess up? I figure while the dash is apart I can work on straightening out some of the wiring and sand and maybe spraybomb the sheetmetal behind the dash area.

Once again, appreciate the help. This just happens to be "one of those days" where one thing led into another.

Mark

[Restrorob]

Mark,

I'm not sure how you would go about cleaning the rust off those connections, I do know if your not very careful you can damage the copper ribbon. Also, I really don't think cleaning the rust on the outside area will do any good.

IMO, I'd generally clean the cluster and maybe put a little die-electric (nygel) grease on the rust areas to help keep it from getting worse. Then try the new sending unit and see what happens. If it's still no go make sure the wire from the gauge to the sending unit isn't shorted to ground, If not start looking around for another cluster. Used gauge clusters aren't very expensive but the tach clusters are.

Good Luck

[TheSleeper]

i just put a short pipe nipple and a brass 90 on my 87 to clear the hei distributor, sorta angled it back towards firewall and drivers side.

cant give ya any better advice than given on the cluster. one truck i had with a bad one, the plastic was so deteriorated it just crumbled in my hand. i did not have any choice but to replace it, i pulled a used one that was in decent shape from a truck at a pull-a-part place.

[RuralRoute C-30]

I tend to agree about looking for another cluster. The plastic that has the circuits is just too brittle to even try to clean off. Since I am not needing this truck at this time, figure it best to look for another cluster, or even if I could find at least an 80's rear half of one. Gauges are probably ok. Yet would rather take the time and do it right, clean up the wiring, the sheet metal and such while I can.

Have a radio coming anyway and this will make it easier to install that as well.

Plan on picking up those brass fittings this week while in town at the day job. Hope to get the sender unit installed and will be looking for a decent 80'[s gauge cluster in the meantime. Saw some on ebay and will try some other sources.

I am glad to have found that mouse nest! That could have been a potential cab fire hazard left as it was in and around all that wiring. That would have been bad!

Overall, not a bad day, I learned how to remove the gauge cluster! (and discovered it ain't coming out until that speedo cable is disconnected! )

Thankful for this forum and the advice...it sure helps!

Mark

[RuralRoute C-30]

Well this project has gone full circle. Everything back together with the 'new' old cluster with the newer circuit panel and oil pressure gauge works as it should. Even cleared out all the wiring from its life as a wrecker and installed the 'new' radio. (there was a lot of wiring to address and the mice did eat the speaker in the dash! New one under the seat for now.)

Just some pics of today and the final product. I was going to spray paint the black cover but too cold and the wife would have been more than annoyed if I tried it in the house!

Anyway, it works and the truck is back on the road today. Did a few runs with it to confirm and filled the tank to see that gas gauge move. I think the speedometer is around 5mph off but I am taking a break from a long week in the shop every night on this project.

So "at this time", a phrase I have learned over my years to say, it leaks no oil, oil pressure gauge works, and it runs good!

Only have had this truck 5 weeks so far and still going through that "getting to know you" period!

I am looking forward to tonight to check on how the LED's in the dash look.




and #0000steel wool and some minor work turned the black plate in the heater control cover back to this, will see what it lights up like tonight.

Finally out of the shop! (at this time)


Mark

[Restrorob]

Originally Posted by RuralRoute C-30

I am looking forward to tonight to check on how the LED's in the dash look.

That's a fine job right there, It'll probably blind you now with the LED's and silver/chrome back ground !

[raws67]

The best way that I have found to clean those ribbons is with a pencil eraser. By the way we have a field behind my house and we used to have problems with mice doing that same thing. I ended up scattering bounce dryer sheets under the dash and under the seats and have never had a problem since. Something in the sheet pisses them off and they will stay out. Im just thinking if you had this problem once it would suck to put all that work into having them return and rebuild a new nest. Just a thought

[RuralRoute C-30]

I'll remember that. Actually I bought this truck 5 weeks ago. It had sat for a year before the guy I purchased it had got it. An inherited "hidden agenda" was the discovery of the past mice...always gotta love buying used!

It still is worth it.
Mark

[kikkegek]

interesting thread. I have an oil guage that moves to the 15psi as soon as I start the engine and then stays there all the time while revving from 700 - 3.000 rpm....so I need to check my guage and sender too....thanks for the advise at the beginning of this topic...