1972 AMG M35a2 oil pressure gauge problem

[CNKILLERCLOWN]

I have a 1972 AMG deuce and as soon as you turn on the ignition switch the oil pressure gauge pegs out. The oil sending unit was taken out to plumb in a gauge under the hood. What would cause the gauge to do this? I would like to fix this and get it back original. Anyone have some pointers on what could be jacked up or what to look at? The sending unit isn't hooked up and is in a box under the seat so isn't part of the equation.

 

[sandcobra164]

There is a cut in the insulation of the wire providing a short straight to ground or you have a bad sending unit with an internal short. To determine which it is, unplug the wire from the sending unit and at the gauge end and using an ohm meter, check for continuity to ground. If that passes, go to the sending unit itself and check it for continuity to ground. You should find what your looking for with those two tests and have an idea of what needs repairing.

 

[CNKILLERCLOWN]

With the sending unit totally removed from the equation it is still doing it. Ill hit it with a meter and report back.

 

[Reaper651]

Yup it sounds like your sender wire is grounding out somewhere. This is also a way to test to see if its the gauge or sender when trying to diagnose a gauge not working. Unplug the sender wire at the sender and ground it, if the gauge jumps then its probably the sender.

 

[CNKILLERCLOWN]

As I stated the sending unit is in a BOX under the seat and is removed from the circuit and removed from the engine. Obviously it isn't plugged up.

 

[Reaper651]

As I stated the sending unit is in a BOX under the seat and is removed from the circuit and removed from the engine. Obviously it isn't plugged up.

Yeah I got that. I was just saying that's a way to diagnose which is bad if the gauge is NOT working. You say your gauge is pegged when the acc. switch is on. This will happen when the sender wire is grounded. Also, Try unhooking the sender wire from the gauge and see if it still pegs out. It sounds like your sender wire is going to ground somewhere. It could be shorting out where your harness goes through the firewall. I'm also diagnosing gauge issues on my truck. Lol it is So much fun.
Good luck.

 

[CNKILLERCLOWN]

Obviously I ain't the only cat with this problem then... I had also noticed a lot of the rubber connector boots on this truck have issues as well. Ill check it with the sender wire removed from behind the panel and see what happens. Any clue were to get a bulk bag of the connector boots?

 

[Reaper651]

TNJ Murray, Eriks Surplus e.t.c has the connectors and boots. The problem is I think you need to replace the whole end but Im not totally sure on that. The connectors are very reasonable though. The crimping pliers are a little more pricey but worth it IMO. I need to get a set of these soon. When you take the connectors off, twist the boot to loosen it up before trying to remove it. This usually works but sometimes the boots will still break. Also, make sure you put a bit of grease on the male end of the boot, then they will come off easy next time.

 

[CNKILLERCLOWN]

The number 27 wire is grounded. I also checked the base of the sending unit base to the pin and it showed continuity. Is it supposed to?

 

[doghead]

This should be covered in the -20 level TM.

 

[CNKILLERCLOWN]

I don't have it and it takes too long to download it and is a pain to read on my phone.

 

[doghead]

Well, if you want to fix your problem, you could always go somewhere and use a computer.

I never let the shortfalls of my phone stop me.

 

[CNKILLERCLOWN]

Hence the reason for just asking for the information out in the open. Save the problem of digging. I seriously doubt I am the only cat that has been down this road.

 

[doghead]

There is no reason to copy and post the TMs, when they are readily available.

The TMs have a step by step troubleshooting section just for the gauges.

 

[CNKILLERCLOWN]

Great I didn't ask that they be posted. I asked a simple question and posted that the number 27 wire is grounded. I am not going to download the TM to my iPhone and don't have access to the computer. I am asking for HELP in the open. I am NOT able to look at a TM at this time. Info is all I want. Is the 27 wire supposed to be grounded or open? Not a hard question to answer. Likewise is there supposed to be continuity between the frame and the pin of the sending unit. No sense in making a situation into something its not. If you don't have the answer then step aside.

I am a firearms tech by trade and could tell some cat to go read the TM regarding headspacing and timing the Ma Deuce and hope the guy does not kill himself when his gun blows up or I could just tell him the info so he gets it done. Really simple..

 

[doghead]

I got 538 results with an advanced search for " oil pressure gauge pegged". In the first page of results, I found several threads that probably would help you.

Here's one, http://www.steelsoldiers.com/showth...Oil-Gauge&highlight=oil+pressure+gauge+pegged

Can you search on your phone?

 

[doghead]

If you don't have the answer then step aside.

Wrong answer, that is not how this site is managed.

Maybe someone will read the TM to you. As I said, the info is there, in a step by step format and will solve your issue. If you want the CORRECT info, it is in the TM.

If you want members guesses or less than reliable memories, well, hang in there and someone else may offer some ideas.

If you want to use the Forums, I suggest you take advise from the Moderators and use the site and it's resources and use it as we manage(guide) it.

 

[jbayer]

Open circuit causes gauge to peg, not shorted.
Ground the sending unit wire, as in shorted, makes it read zero.

 

[CNKILLERCLOWN]

Wrong answer, that is not how this site is managed.

Maybe someone will read the TM to you. As I said, the info is there, in a step by step format and will solve your issue. If you want the CORRECT info, it is in the TM.

If you want members guesses or less than reliable memories, well, hang in there and someone else may offer some ideas.

If you want to use the Forums, I suggest you take advise from the Moderators and use the site and it's resources and use it as we manage(guide) it.

I would figure someone here had either been a mechanic on one of these or had the problem before. I am pretty proficient at most mechanical stuff. Hence the reason I posted the two specific things based on what the other two suggested. While I can't read the TM in my current situation I suspect someone might have the knowledge as to which one of the wires should show an open circuit and if the sending unit should be showing continuity between the frame and the pin. I would venture to say the answers there would not be a guess. If the site is managed a certain way that's fine, being anal retentive when a user is having a problem and has a restricted means of using what's available here isn't being very helpful and certainly isn't warranted. I have no way to look at a TM short of someone mailing one to me and would like to get this problem resolved before I have to run it a few 100 miles next month. This is a 60 PSI guage and sendin unit BTW if that means any difference in the way it might work.

 

[CNKILLERCLOWN]

Open circuit causes gauge to peg, not shorted.
Ground the sending unit wire, as in shorted, makes it read zero.

I am assuming one side would go to ground and then the other side would be variable based on the variance of what the sending unit was sensing?