Fuel and Trim gauge issues

[81 Checkmate]

1981 Checkmate.......898 wiring harness...pre BPA wiring code.

After restoring the boat and putting in rebuilt motor....350 in place of 305. Got it fired up yesterday...all good exept the trim gauge and the fuel gauge both peg.

Fuel gauge reads full....tank was empty and put in 3.5 gallons, could be a bad gauge...if you tap on it...it will jump down.

Trim gauge reads full up.........dont have trim rams hooked up...so transom bell houseing is in a loose position.

Not sure if i have the sender wires hooked up right.......I have orange/brown under dash coming from gauge to a little block thats mounted at the harness plug bracket.......then the two wires both black from the sender going to the same little block.

I have the schematic for the wiring......but its hard to make out how/what the sender wires hook up.

Thanks.

 

[glenn property of pam]

Re: Fuel and Trim gauge issues

fuel gauge and trim sender are both referenced to ground and as a added bonus both ground wires are normally connected in the rear of the boat near the motor. Either you have a ground problem at the dash (ground buss is disconnected or corrosion, If you have a volt meter and that is working correctly then it probably not the problem) or you have a ground buss near the motor that is disconnected or has corrosion and since you have pulled the motor that the first place I would check. Follow the black wire from the trim or fuel sender and see where it goes. they should go to a buss then back to the battery negative.

 

[81 Checkmate]

Re: Fuel and Trim gauge issues

Checked out the grounds....Looks like the gas tank and sender are two different ground wires goin into the harness. No bus bar at motor for grounds or under dash.
Grounds are all linked together at dash.

I took some pics.

the gauges....purple wire comes from harness to gas gauge then jumps over to trim gauge to the up terminal.... Orange/brown wire from harness to the trim gauge to the down terminal.

the wires at the block on harness plug bracket....purple wire from harness and orange/brown wire to block........the two trim wires from sender...both are black going to block. So all 4 wires are mounted on the same block touching each other.

The wires at the gas tank.

Hope this helps! Thanks

 

[81 Checkmate]

Re: Fuel and Trim gauge issues

Anyone?.........I realy wanted to know if i have the trim wires hooked up right at the motor.

 

[glenn property of pam]

Re: Fuel and Trim gauge issues

Ok from what I am seeing the grounds should be made up near the motor. It may be a bolt. One black wire should go to the ground bolt the other should be joined to the harness on the brown/white wire that goes to the sender terminal on the gauge. Im confussed that you said that a wire goes to the up terminal and down terminal of the trim gauge as there should not be and terminal marked up and down. Also the grounds at the gauge are for the lights and the electronics in the gauge. They use the ground system to join the wires from the trim so I do not think that the ground wires would run all the way back to the dash. Look at this link and see if it helps any

http://www.boatfix.com/merc/Servmanl/13/13E4R2.PDF

P.s trim wiring is not connected to the trim gauge if that what you are thinking.

 

[81 Checkmate]

Re: Fuel and Trim gauge issues

Yes i can be confusing..........

Just looked at the trim gauge wires........the purple wire goes to the terminal marked POS, not up (Duh)

The orange/brown goes to the terminal marked sender , (Not down)

I never did disconect the wires at the dash...i kept them all hooked up......but the trim gauge never worked before i restored the boat.

So the purple wire at the engine.....its on the engine side of the harness..not the key/gauge harness from the dash.

The orange/brown wire is with the dash harness going to motor...?

Sorry for the confusion......also i have a amp meter..no volt meter.

 

[81 Checkmate]

Re: Fuel and Trim gauge issues

I think i have the gas gauge figured out.......with the key on and you bang on the tank it comes down to quarter tank.....then back up. So its in the sender in the tank.

Im gona wait till i get a half tank or so and see if it just might be stuck......no biggie

 

[81 Checkmate]

Re: Fuel and Trim gauge issues

P.s trim wiring is not connected to the trim gauge if that what you are thinking.



I have the trim wires hooked up to the pump as they should be.......it works at the shifter!

 

[81 Checkmate]

Re: Fuel and Trim gauge issues

Thanks for the link.....its a little different color code but the same Principal.

After doing some research and reading i am going to try this tonight.....I think i have it figured out!

 

[alldodge]

Re: Fuel and Trim gauge issues

Thanks for the link.....its a little different color code but the same Principal.

After doing some research and reading i am going to try this tonight.....I think i have it figured out!


View attachment 213076

Agree with your propsed connections except the purple wire. If you connect the purple wire to a red hot lead you will be hot wiring your boat. The red wires go through the circuit breaker and change to red/purple. The red/purple goes to the key switch and when you turn the key it supplies power to the purple wire. The purple wire may have gone to the choke on the carb or something else like it.

 

[81 Checkmate]

Re: Fuel and Trim gauge issues

Yes agreed too........After i got home looking at it...i did not hook purple wire to positive,that wouldn't make sence.

So i disconected purple wire from terminal block.....just had the orange/brown wire from gauge and black wire from sender, then other black wire from sender on a engine ground.......No change, still pegs full up.......flip flop black wires from sender....no change!

With purple wire dsiconected...turn key on and checked voltage on purple wire and it reads 0 volts...have not checked it while engine is running tho.

So i traced the purple wire again at the dash......from engine to dash, goes to a plug under dash... then changes colors to a pink wire on other side of plug...then looks like it goes to ignition switch or to the in-dash fuse for the bilge pump. Of corse there are two pink wires and its hard to tell which one is the one.

Im am so confused....By the way i hate wiring......not one of my best assest! Why in the world cant they keep all the wires the same color from dash/gauge to engine!

Everything else works......Bilge pump/ blower motor, Amp meter, oil pressure, temp, tach......even the lights work...also the trim pump!

I give....

 

[alldodge]

Re: Fuel and Trim gauge issues

The purple wire should go hot when the key is turned to run, but for now I would leave it disconnected. You mentioned you did not remove any of the wires on the gauges, with that disconnect the sender wire. The pictures previously posted I see what appears to be some corrision. If the wire is not insulated from the bracket it could be going to ground. After disconnetion and making sure no other connection is being made touch the wire to the stud. If the meter still pegs try rotating the sender, if moving still pegs the gauge then I'm thinking you may have a bad sender.

 

[81 Checkmate]

Re: Fuel and Trim gauge issues

I see grasshoper...... Well i did take the wires off the gauges...

I had made new dash panels to replace the old warp up ones. When i put the gauges on the new panel i did them one by one and kept the wires on the same terminal location.

If you look at the back of the gauge picture you will see that in-between the two gauges that there is a tilt/trim old style toggle switches from the factory??so at some time or another someone switched the shifter out with the quick silver panel mount and added the trim gauge?therefore added the sender wire to the harness going to motor?. The sender wire is on the outside of the harness bundle.

Lets get this straighten out first then back to purple wire.....

Thanks Alldodge

 

[alldodge]

Re: Fuel and Trim gauge issues

Ok sensei my mistake, it is time to catch fly with chop sticks

Have you tried moving the sender on the drive?

 

[81 Checkmate]

Re: Fuel and Trim gauge issues

Not yet.....that will be my next move. I have a few hours tonight after work before Thirsty Thursday starts!

I was going to replace all the gauges before now...but it wasn't in the budget, plus i was trying to get the boat on the water before winter this year..... and thats not gona happen. But in hind-sight im working out the bugs....

Im wanting to replace all the gauges this winter and with the way the gauges are set up...all i have to do is pull off the entire panel and replace the gauges one by one..... Easy - Peasey

Will let you know how that works......

Back to the purple wire... So you are saying it should have 12 volts while the engine is running and no volts with the key just turned to on?

I dont have an electric choke...but there is a tan wire with a clip plug there for it on the harness and i have it taped off.

 

[alldodge]

Re: Fuel and Trim gauge issues

The purple wire should provide 12V when the key is turned to on, wheather the engine is running or not. The red battery lead goes to the starter, from the starter it goes to the main engine breaker. From the breaker wire chages to red/pur and goes to alternator, starter slave relay and up to key switch. The key switch goes to ON (or run) this energizes the purple wire which supplies 12V to all circuits used by the engine and gauges. Key is turned to start which passes 12V to yel/red to start engine.

 

[81 Checkmate]

Re: Fuel and Trim gauge issues

Yup ....thats the way it's set up on the motor...same colors to.

Thats what's confusing........the purple wire has no volts with key on and it should be hot. There is a purple wire at the canon plug coming from the dash

So i need to double check the purple wire at the dash....if it's not hot now then it's not hooked to anything.

Thanks Alldodge!

 

[glenn property of pam]

Re: Fuel and Trim gauge issues

do me a favor and check the back of the gauges to make sure that the sender and power wire have isolation washers as the first picture shows something between the sender post and the bracket that maybe build up/grease?. The bracket uses the posts for support but should not make a electrical circuit.

 

[81 Checkmate]

Re: Fuel and Trim gauge issues

Checked the post.......had a bunch of fuzzy fiberglass dust and greasey...and it has the rubber isolation washer on bracket... so i cleaned the post - put wire back on same thing. Took wire off as Alldodge said and the neadle went down......just touched the post with wire and neadle full up.

Went to outdrive and rotated sender puck...no change/full up. Took cover off and it was very clean inside...no corosion..put cover back on. No cuts on wires either..... Removed the whole sender to look at back side and it was very greasey where the short shaft fits into the gimble ring...I guess becouse there is a zerk fitting there. Put back on no change!

Looks like the sender is bad....Ill have to wait untill i do a bellows job and replace it.

Good news i fixed the gas gauge.....took the sender out of the tank...took it apart and cleaned and stretched the little post spring to make better contact with the reastat spring. Reasembled and it work's....... Also i need more fuel...bone dry :facepalm:

 

[alldodge]

Re: Fuel and Trim gauge issues

Looks like your making progress, but before you replace the sender put an ohm meter across the two wires and rotate the sender. If it stays zero ohms the sender needs replacing, if it goes up and back to zero it doesn't.