Help with Sensor changes on 2001 Challenger 1800

[Chunkeymonkey]

Hello,

I would like to change out the air temp sensor, the head temp sensor, and the coolant temp sensor on my 2001 M2 V6 Jet Drive Challenger 1800, as I have read this is a relatively quick/easy/cheap first fix if i am not getting full power (35 mph max at the moment). Can anyone provide on advice, pictures/instructions etc. on doing this job please as i am a noobie, and not the most mechanically minded.

I would also be grateful for a parts guru to qualify my part #'s below are for my model/year boat (my engine serial number is 0E386098). I am ordering these from eBay, but if there is somewhere better to order parts for my boat from, i am all ears

Mercury Marine/Mercruiser New OEM TEMPERATURE TEMP SENSOR 13221T01
Mercury Marine/Mercruiser New OEM TEMPERATURE SENSOR-TEMP SENDER 13536A14
Mercury New OEM Engine Block Temperature Temp Sender/Sensor Unit 974651; 97465 1

Thank you in advance!

 

[Dr Honda]

Before replacing them... grab a meter, and check them. It get's expensive just throwing $$$ at a problem.


SO... lets talk about your problem.

Speed means nothing to me. SO... at full throttle... what is the RPM? Is there any stuttering? (like you are losing spark) Have you simply looked in at the engine, and verified that the throttle is actually opening all the way? Have you checked your ignition links to make sure they are moving? Have you checked the engine compression?

 

[Chunkeymonkey]

Hi Dr. Honda, thanks for the reply, and i apologize up front as i may be one of your more difficult assignments...:facepalm:

I do not really want to throw $$$'s at the problem, but this seemed to be related from reading other posts to what i am experiencing, and one of the cheapest route to go before taking it to the shop (and easiest for someone of my limited knowledge). As i said in my post, i am a noob, but I am very open to trying to a point that does not take me even deeper down a hole

I will get the RPM's at full throttle and post back tomorrow. From what i can make out, there is no stuttering when i am going full bore. I have looked at the engine to see if there was anything obvious (lose/detached cables/wires), but nothing looks out of sorts.

Is there a specific tool i could buy to check the compression, or any reference in a shop manual, and the same for checking the ignition links?

Thanks again

 

[Dr Honda]

Since you are a premium member... down load the M2 240 efi manual. (not the 2002 version) That will help you.


Yes... there is a compression gauge you can buy. But some of the cheaper ones don't work well. Try your local auto parts store, and see if they loan tools. It's a simple test. You pull a spark plug, thread in the tool, hold the throttle open, and crank the engine a few times. (don't start it ! Pull all the spark wires) Then read the gauge. 125~135 PSI is a happy Mercury engine.


Lets get the peak RPM and go from there.

 

[Chunkeymonkey]

Hi Dr. Honda - just got back from the tests...

Firstly the compression test. I brought a tester from autozone as they would not loan one. On the right side (looking out to the back of the boat), i was getting 120 psi. On the left side, i was getting 122 psi. This was consistent across three times i run on each. I also took some pictures of the pulled plugs in case this helps in any way?

I then took it out for a run, and I was getting 35-36 mph at 5000 RPM's - no stuttering.

I also took some pictures of the pulled plugs in case this helps the diagnosis in any way?

Thanks again for the help :thumbsup:

 

[Dr Honda]

OK... 120 is a tad low... but right now we will just assume it's the gauge. (but it's even)


BUT... 5000 RPM is low. You have a cyl or two not firing. So... get a couple in-line spark testers... and go out for a ride, and find what cyl's aren't firing.

Alternatively, you can go for a short ride, and use an IR temp gun, and scan the temps of the metal parts of the spark plugs. The dead cyl's will be cold. (ish) I use to tell people to just touch the base of the plug... but I don't want to get yelled at if you burn yourself. (LOL)

 

[Chunkeymonkey]

Thanks Dr. Honda, i will go the in-line tester route - no burnt fingers for me

I'll post back as soon as i have them...

 

[Chunkeymonkey]

Hi Dr. Honda, just got back from the spark test, and all were ok? I placed an in-line spark tester on each plug, started the engine, and everyone showed the flickering light in the tester...

 

[Dr Honda]

Did you check on the water, at higher throttle settings? or on the trailer?


When you get a dead cyl or 2... the engine will run smooth, but the peak RPM's are low. Also... when was the last time you simply put in fresh sparkplugs?

 

[Chunkeymonkey]

I checked at the dock (started engine and then turned off), not underway...Do i need to check in-line spark again with the engine under load?

I have not put plugs in since i have had it (approx 6 months). From the pictures i sent, did they need changing, or is it just a matter of course in troubleshooting this - could it be as easy as plugs?

If i do put in new plugs, do i need to get the below (i pulled this from the service manual), or are there other generics i can get from Napa, Autozone etc.?

NGK BPZ8HS10
1mm Gap

Thank you again for the help here!

 

[K Rock]

The NGK are the best for it, I bought mine at Advanced Auto Parts. It was the least expensive in the area, and definitely a must on the new to you list. There is no telling how old yours are and just good measure to replace them and eliminate the possibility of bad spark.

 

[Dr Honda]

Yep, advance has them, and they aren't too expensive.

Time wise... you are fine... but when you are having potential ignition problems... it's good to have fresh plugs.

Yes... you need to check spark with a load, and running at the speed that you assume there is an issue. That means... full power.

Last question to you.... what speed does your engine idle at?

 

[Chunkeymonkey]

Thanks for the advice K Rock, i will order some up now...

 

[Chunkeymonkey]

Hi Dr. Honda, i will change out the plugs, test spark again under load, and report back (they are out of stock locally, so need to have them shipped)...

Thanks again

 

[Chunkeymonkey]

Hi Dr. Honda, I changed out the plugs and tested for spark again under load, all were showing spark. The engine idles at 1000 rpms.

What would be the next area to check, and is there a tool that you can use as a diagnostic?

Thanks again

 

[Dr Honda]

On the early 240, there isn't a good diagnostic tool. But even on the new engine... the ECU would have to throw a code before the tool would help.

So... 1000 RPM is also a tad low. But it's close to spec.

Have you verified that the throttle opens full at the engine?

 

[Chunkeymonkey]

Thanks again and no, how do I do that, or is this something I can get from the manual?

 

[Dr Honda]

Just put your head in the engine compartment, and have someone open the throttle lever. At the engine... make sure the linkage is moving to it's full travel.