2001 Mercury 240 EFI not firing all the cylinders

[eugene69]

Hi everyone. I bought Challenger 2000 last fall and did not have a chance to start it until last week. Although the previous owner claimed that it worked fine, it would only fire on 3 cylinders. In the shop they told me that 2 cylinders do not have spark and one does not fire for another reason. Cylinders 2, 4 and 5. The engine starts, but on idle sounds terrible. Will try to attach the short video to demonstrate. They are too busy at the shop and suggested I take it somewhere else Before I do so, decided to try fixing it myself. Anybody can lead me to the best troubleshooting technique? Thanks in advance.

 

[Tim75]

Do you still have the throttle guardian in the driver helm box?
Disconnect the black with yellow stripe wire and check again. Or find same wire, on top of engine, aft of flywheel. Disconnect and try again.

 

[Dr Honda]

Welcome to the board.

First... it's a 2 stroke engine... and they will sound rough without a load on them. So, before jumping to conclusions... I would put in a fresh set of spark plugs, and take it to the local lake. You may find that when it's loaded... it runs fine.

Second... the 2 wires are for gauges that seadoo did not use. Keep in mind that Seadoo bought those engines from Mercury, and that engine was not specifically made for them. So... those are not an issue.

Lastly... as Tim said... look for a throttle guardian. It will be a black box up in the helm. It's there to keep it from reving too high in N or R. But, they go bad, and cause all kinds of issues. We always recommend removing it.

 

[eugene69]

Tim, Dr Honda - Thank you for your replies. I will try removing the guardian today and will let you know. And thanks for the info on the two hanging wires - did bug me a bit I did take the boat to the local dealership in the fall (to winterize) and they told me that the bilge fan was not working and need to be replaced. When I decided to remove it myself to see what could be wrong with this simple device, it turned out to be disconnected.. So this two hanging connectors looked quite suspicious. But now I know.

 

[eugene69]

Oh, by the way - another quick question. I was told that I need to start engine first and then (almost immediately) supply water to it. And shut down water first and then the engine. Is that correct procedure? Can engine run for a minute or two without being flushed with water?

 

[eugene69]

Disconnected the wire that I think is the one going to the throttle guardian (on the video it shows) and still not all the cylinders are firing.. I want to test if all the plugs are getting voltage for the spark - what would be the easiest way to do so? Are there any harnesses that will plug in instead of plugs (or inline) and will indicate if there is voltage applying? Sorry for all the silly questions, but I have never done this before.

 

[poppie]

In line spark testers are available at any auto parts store. They run about $7 each.

 

[eugene69]

Got tester (Thank You!) and sparks 1 and 4 are not getting voltage. Swapped CDMs (1 with 3 and 4 with 2) - problem stayed with the cylinder. This tells me that the CDM is NOT the issue... What else could it be? What should I look at next? Any ideas would be greatly appreciated.

 

[Dr Honda]

OK... not sparking on 1 and 4... doesn't follow the CDM.... it's the pickup coil under the flywheel. OR... one of the wires got chaffed. So... pop off the flywheel and take a look.

 

[Tim75]

You can test the trigger coils easily. Procedure is in the book. It does seem that one of the three coils on it is dead. The connector is aft of the flywheel, on a bracket. Is the insulation good or crumbly? If it's crumbly, you have the original trigger. Time to replace it. If it's not bad now, the insulation will cause you issues later. You will need a new trigger and Merc flywheel puller. Both on ebay.

 

[eugene69]

Thank you! Yes, it seems to be the trigger. I did measure impedance and it shows 0.129 on the other two coils and "opened" on the one that serves the two cylinders that wouldn't fire (wires blue and purple). Will attempt flywheel removal and replacing the trigger. Will let everyone know when done. Need to order parts first.

 

[eugene69]

OK. It was the trigger assembly - did replace it and now have spark on all the 12 plugs (just kidding - 6 of cause ). The engine sounds better now, but still I would expect something more "solid" I would say. Hard to explain.. Will try putting the boat into the river in the next couple of days. Meanwhile - what are other tests that I can perform on the engine to make sure it works as per specs? Like compression or timing? I did order DMT 2004 Tachometer on EBay for 300$ - sounds like a good deal and I will hopefully be able to run some more complex testing. Can someone recommend any other testing that can be done "at home"? I would love to run them to make sure there is nothing else to address. Thank you. Hey,- ordered flywheel holder online, but never got it, so had to make my own tool. Want to share it with everyone. Here is what I used to remove the nut holding the wheel:

 

[Tim75]

If you are expecting it to be as smooth as a V8 at idle; it won't. 2-stroke engines do not run smooth at idle or without a load.

You got the nut loose. OK. How did you break the flywheel loose from its taper?

Compression check can be done. Must be done at WOT and all plugs out. You can also test the TPS. Many threads here about that. Check fuel pressure at the "tire" valve on top of the VST.

Compression: should be above 120psi. Fuel: pressure should be 35-37psi.

 

[eugene69]

Oh, I did get (and used) the puller. I just didn't receive the flywheel holder on time. Thanks for the tips on additional testing - will try to run them. But first - will put the boat in the water tomorrow. Will see how it goes.

 

[eugene69]

OK - I launched the boat today and unfortunately didn't go anywhere... The engine started fine, but after running for about 2-3 minutes it did stall on me. Wouldn't restart right away, but after waiting for a minute or two it would start. This time would stall almost instantaneously. If I try accelerating it would not make any difference - same sound and stalls... Bad gas? I got full tank in the fall and didn't ask when it was filled and which fuel. At the marina they just added stabilizer for the winter. Could it be the case? Anything else? On the video below it does show the engine stalling (I keep saying "idling" for some reason ). Any ideas?

 

[rsatina2002]

check your air temp sensor too... and port side temp sensor... and check also the specs of TPS.... mine was like that before, it stall after running for 30 mins and it won't start and rest for about 30-45 mins it'll start again and realize my air temp sensor is not functioning when I do my Ohm temperature test.... Check it out... Sounds like your engine is firing well. Make sure you have all the sparks and 120 PSI on all cylinder and check your port temp sensor, air temp sensor.... lastly the electronic fuel pump in the VST pressure.

 

[eugene69]

Thank you, I will check. If it comes to draining the existing gas - is there any way to do so? I did try in the fall, but couldn't get into the tank through the main hose (something is blocking inside). And couldn't find anything in the manual...

 

[eugene69]

check your air temp sensor too... and port side temp sensor... and check also the specs of TPS.... mine was like that before, it stall after running for 30 mins and it won't start and rest for about 30-45 mins it'll start again and realize my air temp sensor is not functioning when I do my Ohm temperature test.... Check it out... Sounds like your engine is firing well. Make sure you have all the sparks and 120 PSI on all cylinder and check your port temp sensor, air temp sensor.... lastly the electronic fuel pump in the VST pressure.

Thanks again - do you have part numbers for the both sensors by any chance? I think it is a good idea to replace them and they shouldn't be expensive. I found one sensor in the catalog (8285861 Water Sensing Probe - Mercury Marine | Crowley Marine) but now sure if that is the sensor you mentioned.

 

[Tim75]

Thank you, I will check. If it comes to draining the existing gas - is there any way to do so? I did try in the fall, but couldn't get into the tank through the main hose (something is blocking inside). And couldn't findyour gas anything in the manual...

There is definitely a blockage in the fill pipe. Makes it harder for someone to steal your gas.
You will need to either remove the fill pipe from the tank or remove the pickup tube. Then you can siphon out the old gas.

Has your VST been serviced lately? he inlet float needle sometimes corrodes in place and only lets in a tiny amount of gas. Enough to run the engine for a few seconds. Several threads here about testing and fixing.

 

[eugene69]

Got new sensors (air and head engine) and now have question - does it matter which pin goes where? There are two pins on the air filter, for example, and they are not marked in any way (same wire color). Can I connect them to either one of the corresponding connectors? Same for the head engine sensor - 3 contacts, one is different and you can't go wrong. What about the other two?
And I still want to try supplying new gas to the engine from the portable can (I have 20L can that I am using for my outboard). Just to eliminate the possibility of bad gas... Actually even the manual (page 3D-19) suggests exactly that - called "Fresh quality fuel". But unfortunately it doesn't say where should I connect that portable tank. Any suggestions? Thank you!

 

[Tim75]

Got new sensors (air and head engine) and now have question - does it matter which pin goes where? There are two pins on the air filter, for example, and they are not marked in any way (same wire color). Can I connect them to either one of the corresponding connectors? Same for the head engine sensor - 3 contacts, one is different and you can't go wrong. What about the other two?
And I still want to try supplying new gas to the engine from the portable can (I have 20L can that I am using for my outboard). Just to eliminate the possibility of bad gas... Actually even the manual (page 3D-19) suggests exactly that - called "Fresh quality fuel". But unfortunately it doesn't say where should I connect that portable tank. Any suggestions? Thank you!

Air filter??? There is no air filter.
If 2 wires from the same component are the same color and have the same sex connector, they don't matter which way they connect (to the proper harness).

Think about this: a basic on-off switch. It does not matter which way the wires go.

Fuel test tank would connect where the hose from the main fuel tank connects to the lift pump. The one that thump-thump when you turn the key on. Disconnect that hose, and plug it with something that can be sealed. If you are careless, you may fill the bilge with gas!!! Connect you test tank hose to that filter. Should be good to test.

 

[eugene69]

Thanks! Air sensor, of cause.. Did not install them yet, so no updates - will try over weekend.

 

[Hawk111]

Oh, by the way - another quick question. I was told that I need to start engine first and then (almost immediately) supply water to it. And shut down water first and then the engine. Is that correct procedure? Can engine run for a minute or two without being flushed with water?

I do 30 seconds tops.

 

[eugene69]

Air filter??? There is no air filter.
If 2 wires from the same component are the same color and have the same sex connector, they don't matter which way they connect (to the proper harness).

Think about this: a basic on-off switch. It does not matter which way the wires go.

Fuel test tank would connect where the hose from the main fuel tank connects to the lift pump. The one that thump-thump when you turn the key on. Disconnect that hose, and plug it with something that can be sealed. If you are careless, you may fill the bilge with gas!!! Connect you test tank hose to that filter. Should be good to test.

OK, Replaced air temperature sensor and head temperature sensor, but decided to take it to the marina regardless to check. Asked them to put it in the water. Got call from them this morning advising that the high-pressure fuel pump is not working and to replace it they need 1200 for the pump and 4 hours of labor. Can fuel pump cost that much? Plus they indicated part number 803505T01 that I can't find anywhere on Internet.. Is it a rip-off? Can engine run even for 3 minutes without operational fuel pump? Sounds like BS to me. Any ideas? On the same note, they did check the compression in my cylinders and here are the numbers (from cylinder 1 to 6): 112, 113, 118, 114, 118, 115. Are these in the normal range? Thank you.
P.S: Did order the fuel pump on E-Bay for $80 (Mercury Marine Fuel Pump + Strainer Filter OEM # 809088T-1 809088T1 8090881 | eBay) - does this look like the correct one?

 

[rsatina2002]

If you are talking about the electronic fuel pump in the VST, yes this is the actual pump, same one that I use my self to repair it DIY through manual specs and guidance... This is the same pump that I use that makes my Challenger run after 5 years of not running at all from the original owner... There is 3 fuel pump on this engine so figure out what fuel pump you are talking about... Most likely this is the most common fuel pump that fails... When you do it yourself, it takes time to remove the VST and just follow the manual specs and proper gaskets to replace so your VST won't leak.... and after changing the fuel pump, check the pressure through the top of the pump with tire pressure gauge it should be 34-36 PSI.