Tps high idle issue! Merc 240

[CURT7TY14]

Help!!!!!! Just installed a new tps in my 01 merc 240 challenger. Cant get the proper voltages on it like my old one and when i go to start the boat it screams the rpm! What am i doing wrong

 

[Tim75]

You installed the tps wrong. Remove it and make sure throttle is at idle. There is a small coupling in there. Don't lose it. After you re-install the tps, move the throttle cam by hand and feel for any binding or hard stop. Watch the throttle plates. If there is, you may have yet installed it wrong. 180º wrong.

Since you can destroy and engine over-revving it with no load, why not make the next test start in the water. You don't even have to take it off the trailer. Leave the stern tied down.

 

[CURT7TY14]

You installed the tps wrong. Remove it and make sure throttle is at idle. There is a small coupling in there. Don't lose it. After you re-install the tps, move the throttle cam by hand and feel for any binding or hard stop. Watch the throttle plates. If there is, you may have yet installed it wrong. 180º wrong.

Since you can destroy and engine over-revving it with no load, why not make the next test start in the water. You don't even have to take it off the trailer. Leave the stern tied down.

I will try turning the sensor 180. I was very convinced i was putting it in the right way but i could be wrong. Will post back tommorow thanks!

 

[CURT7TY14]

Just did a 180 on the tps...same thing. Only getting .10 volts no matter throttle position or turning the tps. Port side sender is unplugged. Ideas??

 

[Dr Honda]

Take the TPS off the engine, and see if you can hit voltages by manually turning it. Also... make sure the throttle is physically shut. The engine shouldn't be able to run away if the throttle body is closed.

Also... make sure you don't have air bleed hoses ripped off. When I did my rebuild, most of the hoses were old and brittle... and a few were broken off the nipples when I pulled the engine.

 

[Tim75]

Just did a 180 on the tps...same thing. Only getting .10 volts no matter throttle position or turning the tps. Port side sender is unplugged. Ideas??

How are you testing? Piercing the wires? Are you sure you are piercing the correct pair? Is your piercing pin actually contacting the inner wire?

 

[CURT7TY14]

How are you testing? Piercing the wires? Are you sure you are piercing the correct pair? Is your piercing pin actually contacting the inner wire?

I made up a set of wires to connect in between the tps and the harness and poked those wires with my dc voltmeter. When hooked up the rpm goes all the way up to 4000rpm and when unhooked the motor actually runs ok and idles around where it should

 

[CURT7TY14]

Wit

Take the TPS off the engine, and see if you can hit voltages by manually turning it. Also... make sure the throttle is physically shut. The engine shouldn't be able to run away if the throttle body is closed.

Also... make sure you don't have air bleed hoses ripped off. When I did my rebuild, most of the hoses were old and brittle... and a few were broken off the nipples when I pulled the engine.

With the tps installed but unplugged it runs ok normal idle rpm but with plugged in it wants to go up to 4000rpm and the throttle appears to be closed! Is the tps that “finicky” that i dont have it set right? Or is the high rpm even a symptom

 

[Dr Honda]

With the TPS unplugged... the ECU will run the engine CRAZY rich to keep it safe. Is it smoking heavy? The TPS shouldn't be finicky at all. Even when not properly set... it should still help the ECU. I'm starting to wonder if you have a fueling issue.

Have you checked the fuel pressure at the regulator?

 

[CURT7TY14]

No i havent...is that the sharder valve on top of the fuel vaporizer???

 

[Tim75]

No i havent...is that the sharder valve on top of the fuel vaporizer???

Shrader valve on top of vst. Should be 36psi.

Sounds like you may also have vacuum leaks. Typically at the bleed hose fittings. There are 10 (I think.) The original hoses cracked and split at the ends where they push onto the delicate fitting pressed into the block. I replaced mine with weedeater fuel hose.

 

[Dr Honda]

No i havent...is that the sharder valve on top of the fuel vaporizer???

yes.

 

[Dr Honda]

Shrader valve on top of vst. Should be 36psi.

Sounds like you may also have vacuum leaks. Typically at the bleed hose fittings. There are 10 (I think.) The original hoses cracked and split at the ends where they push onto the delicate fitting pressed into the block. I replaced mine with weedeater fuel hose.

I used Tygon hoses when I rebuilt my engine. (Yellow hoses) It's heat resistant, and chemical proof. Some of the vinyl based "Weedeater" hoses will only last a few years.

 

[nenikol23]

Sorry I don't mean to pollute the post, but just a quick question for Tony, where does this loose hose connect?

 

[Dr Honda]

Sorry I don't mean to pollute the post, but just a quick question for Tony, where does this loose hose connect?

off the top of my head............

That hose will go to the small nipple on the top of the vapor tank. I will have my head under the deck lid of mt boat later today. if it goes somewhere else... I will repost.

 

[Tim75]

I used Tygon hoses when I rebuilt my engine. (Yellow hoses) It's heat resistant, and chemical proof. Some of the vinyl based "Weedeater" hoses will only last a few years.

View attachment 49350View attachment 49350View attachment 49351

My weedeater hose actually is Tygon. When you ask for Tygon in a store, you will get a "deer in the headlights" look and "What's that?"