UPDATE: cheaper TPS ?????

[Dr Honda]

Hi Guys,

Well... all the Merc guys know, that the Throttle Position Sensor (TPS) doesn't last forever. AND... that it's a $500 part from Mercury.


Last summer, a couple members and I were talking about a cheap replacement. We talked about using something off a car, and making an adapter. BUT... last night... I may have stumbled across the actual part !!

SO... knowing that Mercury didn't have something custom made(they never do)... the search was on to find it's automotive counterpart. From what I can tell... it looks exactly like the 80's, to early 90's Lucas electrical TPS. They were used on some of the Jaguar's and LandRover's. The actual "Case" of the TPS looks the same, with the same "Blade" connection into the throttle body. (FYI: the generic part is TH418)

The only thing I can see that is different is the actual plug on the end of the wires. The Auto version is just bullets, and Merc Probably spec'ed out a "Weather Pack" connector so it was waterproof.


So... right now...


The good news: It's only $125 brand new from RockAuto.com !!!! (not cheap, but better than $500)

The bad news is: I don't have one in my hands to know if it will work.


I'm going to try to find a used one, just to see if they are physically the same, and that they rotate the same direction. If they don't... I'm going to just find the cheapest, common 3 wire TPS out there... and make an adapter.


Here's the Jag version:

 

[Coastiejoe]

I may be able to help you out..

My family owns a salvage yard and we have the digital inventory to just over 1800 other yards.

Let me see if i can find one with a pig-tail.. Will let you know..

 

[Coastiejoe]

Any chance of narrowing it down to a model. In 1984 there were 27 Jaguar models made????

 

[Dr Honda]

The Generic is TH418

Looks like the normal car it was coming from was the mid 80's to early 90's XJS 5.3l V12.


With that said... there was an earlier version that was big, and non-adjustable. That one isn't even close. AND... to do the upgrade on that car... Jag sold an adapter kit. This is the upgraded version. (that's why it's in a red case) There was also a factory unit in a black case, after they changed over to this style, from the bigger version. I will ASSUME that it's the later years. And, I'm also going to assume that the "Black Case" is the same version we have on our Merc engines.

Thanks for looking for me.

FYI... at this point... even a bad one is good to start with. I just need to know if it's physically the same case, and rotates the same direction. With most TPS units... there is a CW and CCW version. But... I can't find the rotaion info on this one, nor can I find if it had a mirror part. (opposite rotation)


Thanks again.

 

[Dr Honda]

Just for ref in this thread... here's the Merc unit.

It looks like the Merc unit has a longer "Snout" where the shaft comes out... but the Jag version has a little rubber seal. So... they may be the same overall length.


Later today... I many make a post on a Jag forum to see if anyone can help with the specs/rotation.

 

[Coastiejoe]

That plug is like many of the versions that GM uses...

I may have to drive to the yard and start opening hoods...

 

[Dr Honda]

That plug is like many of the versions that GM uses...

I may have to drive to the yard and start opening hoods...

Yes. it's a standard "Weather pack", "GM", "delco" plug. But... from what I can tell... GM didn't use this TPS on anything. But... the Weather Pack plugs are very generic on many different applications. (such as boats and PWC)

 

[Coastiejoe]

Found a yard that is 17 miles, (39 minutes driving time) from me that has an 88 JXS which is what seems to be the type you showed in the picture.

He is letting me come take a look at it and if if looks like what you pictured, I will see what I can do about buying it cheap.

Maybe I can "rent" it if we agree to send it back.

 

[Coastiejoe]

BTW, they may both a V8 and a 12 cylinder engine in most of the 80's.. The V8 is the Canadian build. From what I am seeing, they are the same TPS.

One thing to look into is, the V12 has a left hand and a right hand mounted Throttle Body. There is a chance that there are two TPS' on the V12 but no one can answer that just yet. I am only finding the same part number so I am thinking even if there are two, they are they same. If there are different, it would be because of the CW and CCW rotation aspect.

I will let you know what I learn as I go....

 

[Dr Honda]

Thanks for the effort !!!!!!!!!!

A rental is GREAT !!! and I will be happy to send it back. I would only need it for a day to verify the "Fit". I have a bad Mercury unit sitting in my shop... so I could simply measure it... check rotation... and the resistance. (assuming it's still good)

But... cheap is fine too. My thing is... I don't want to lay out $100 for the new one, and find out it's not going to work. More that one time in my life... I think I found something... only to see that it TOTALLY different once I get it in my hand. (like it's half the size of the one I have, but looks the same) But... with that said... I checked the bad one... and the "Blade" is the same shape, and it's sitting in the same position as the red pic above. (it's spring loaded to one side)


I guess one thing to do... before you bother sending it, or getting it from the other dealer...... Hold it in your hand, and while looking at the shaft... it should turn Counter Clockwise.

 

[Coastiejoe]

I'm on the road headed to the yard

 

[Dr Honda]

Thanks again for the help.

So... are you looking at Merc boats... or are you just helping out? Regardless... I'm glad to have some more help in this forum. Not to mention... I have a gut feel, that the other thread you started to help on... this is going to be where his problem is at.

 

[Coastiejoe]

Just helping out,,,

Well, no joy as all the engines they had in stock are good motors and would not remove the TPS from them.

The 1988 Jag XJS mounts under the throttle body and is not in view. We would need to remove the throttle body to get to it. By feel the Bolt holes are straight across and it has a round 3-wire plug with pigtail coming from the TPS. It was slotted and adjustable.

They has one 98 RangRover. Mounted more like a GM but did have the holes straight apart and was adjustable. No pigtail, a direct bolt in application.

I'm not giving up though. I will get out to my family yard and take a look. I can remove anything I want no matter if the engine is good or not.

Do you by chance have a junk one to spare?

 

[Dr Honda]

Thanks for looking.


Are you talking about a junk Merc TPS? I only have the one. But... I could take measurements, and post them for you.

I was looking at the LandRover version... and it's a little different.


AS far as the plug... it doesn't mater as long as it's a pigtail. A direct connect plug is too difficult for most end-users to modify.

 

[Coastiejoe]

I agree,, it is different..

Send or post measurements. I am VERY busy this weekend as I am running in the Tough Mudder and then going back the next day as a volunteer.

I will get out to our yard within the next week if at all possible.

All I can do is try,,,,

 

[Tim75]

TPS issues-- Did anyone ever find out why Merc wants so much $ for this part?

I have found a couple of look-a-likes, but not quite. One maker, VISHAY-SPECTROL out of England, no longer manufactures them, but they are still listed.
10K ohm, 100º rotation, 6" pigtail leads, rated 5,000,000 cycles. Does not list rotation direction. $40 each. Here is one place--http://de.mouser.com/new/vishay/vishay981sensor/

 

[Dr Honda]

Interesting.......


But... the link you sent shows the sender as being a hall-effect unit. So... I'm pretty sure it will have a PWM output, and not a true resistance. But... I guess I can pull the data sheet for it.

If it's has a regulator in it, and outputs a set voltage... that could be good. But... if it's current limited... then it won't work since it's also attached to the port side temp sender.

As far as "Why it's so much"... who knows for sure. But, most boat parts are a 100% mark-up to the dealers. And... since Merc didn't make the EFI parts... they have to make money too. So... there is a 100% markup at each stop.




To All:

I made a post over on a Jag BBS, and they gave me some info. Not exactly what I was looking for... but a bunch of them are converting to a TPS off a Mustang. It would require an adapter to be made... but it's only $20 to $35 on ebay. Yes... it's much cheaper... but if I have to make an adapter... then it will get close to the price of the Jag TPS. Not to mention... if the Jag TPS works... it will only require a plug change, and anyone can handle that.




*******EDIT*******

I'm not sure how you got over on the German site... but I also found it on the USA site. Here's the one that MAY work:


http://www.mouser.com/ProductDetail...9ND4sqHbR69DTc4L78l0BYGZ268qSSLiUcT1YhyMTBA==


It has a flat shaft, and an "Analog" output.



*****EDIT 2*****

I don't think that one will work. It has a max voltage of 5v. I think our computer puts out 12v to the sender. (0~5v is normal logic levels) Also... the shaft style is a "D" shaft... so it would need to be modified to work. And... cutting/grinding on the shaft could destroy the sender.

 

[Mayerichm]

Glad to hear you're working on this. Please let us know what you find out. My boat started smoking and acting funny last year, just metered it out and found that my tps is sending 4.26 volts across the entire throttle range.

 

[Dr Honda]

Hi Guys,


OK... I have a little update.


I made the post on the Jag board... and I got a few responses... but no real answers. Well... after digging around that board... I think I found the answers we needed.


OK... going from one of our members here...

1) the Merc TPS is a 10k unit.

2) From my research... the Jag TPS is a 6k unit.

3) Since they are both liner... the system works as a voltage devider, so the output ratio is the same. (that's good)

4) BUT, since the resistance is lower... the overall current will be higher if we try to use the Jag TPS. (That could be bad) but only maybe.


Here's the deal... after doing a little math... As I recall... the output to the TPS on our engine is 8v. So... with a 10k TPS, the current overall will be 0.8ma. With a 6k TPS it will be 1.2ma.

In that case... we are looking at about 70% MORE current in the system. (that's the bad part) But... since we are still in the "Milliamp" range... it may not make a difference.


In general... while digging around... it's hard to find a 10k TPS because MOST systems are using 5v for the REF.


****EDIT******


Now... this is just math using the TPS straight. Later today... I will go back and look how the port side temp sender is wired in. (that messes up everything since they are calibrated together)



*****EDIT 2*****

I was looking over the manual as I was getting my kid ready for school. It looks like the port side temp sender is wired across the Vref and Gnd. So... it changes the output of the TPS across the scale. AND... it's as low as 400 ohms at full temp. (i think) so the current difference between the 6k and 10k TPS unit shouldn't be a factor.


With that said... I will do the math on the system later tonight.