Challenger 2000 w/ 240 efi (gen1) - can't rev beyond 4k

[ripcuda]

Hi Gang. I got my new-to-me '00 Challenger 2000 with the Mercury 240 efi (gen1, round cover) a week ago. I bought it non-running. Last ran 2 years ago but wouldn't rev up past about 1/2 throttle as the story goes.

Seller was right. It starts and runs great... throttle seems normal up till about 50%... just enough throttle to get on-plane and cruise at 25mph. Throttle above that and it sounds like it's "loading up" (2-stroker too rich)... or there is ignition problems... but it doesn't hesitate or studder or die. I pull throttle back and it seems to run fine at 3800 rpms and boat cruises nicely.

Before I lake tested it (as described above)... I did all the stuff

Compression is good: 135psi +/- 3 in each cylinder.

Fuel system:
- old fuel drained, all fresh 91 fuel (premixed)
- new fuel filter/water-separator, cleaned lift pump pre-filter, cleaned hi-pressure fuel pump strainer
- disassembled and cleaned VST, checked float is good
- rebuilt pulse fuel pump
- tested fuel pressure 35psi primed and while running
- injectors cleaned and tested... good, equal spray patterns in all 6
- new intake manifold base gaskets (to reed block) and intake lid seal gasket
- reeds visually inspected good, none chipped/broken
- oil pump/tanks removed, block-off plate installed, pressure port for oil tank plugged, VST oil-in port plugged, pre-mixing 50:1 (good Quicksilver oil)

So I'm very confident in the fueling system of the engine. It primes as expected and starts instantly (love efi)... even when hot... on the trailer or in the water.

Ignition related:
- new port head temperature sensor
- tested air temperature sensor - ohmed as expected for given temps
- ** tested (ohmed) triggers. All 3 right at 950 ohms... which is just below the min of 1100--1300 ohms. Based on trigger wires/loom, it is not original.
- tested mag stator. All ohms in spec.
- ** found broken/missing ground wires to both Ignition Controller module and Rev limiter module. Fixed both ground wires, both now grounded.
- did not test timing yet. was told it ran great before this can't rev beyond 4k issue started... and flywheel nor timing screws have been touched.
- all wiring hooked up per wiring schematic, all connectors unplugged-cleaned-reconnected
- ** 1 spark plug boot gives my finger a tingle-shock while running... are plug wires/boots replaceable?

Charging related:
- ** One regulator is bad (blows fuse). I've ordered 2 new ones.
- working reg seems to be keeping battery topped off. 14.2v at battery while running 3800 rpms.
- battery is healthy and fully charged, no troubles starting or running
- all fuses good (expect one for bad regulator)... engine fuses

Well that's what I know so far. Next up is testing TPS, confirming timing is good and testing spark at 3800 rpms.

Would failing/bad triggers only affect upper rpms?

Could the Ignition Control module been damaged when it was previously run w/o a ground wire?

Cheers!

 

[ripcuda]

moved from different thread.

If your engine only revs to 4000rpm, you still have an issue. Or 6. Have you done a compression test? All plugs out, WOT. Ideally, 140psi. You may have ignition issues. Do you have 6 spark testers that you can install and test run on the water? How do the spark plugs look? All the same? Some black, some white? You may have injector issues. If you have injector problems, one or more may not be spraying. If no spray, then that cylinder or cylinders are NOT GETTING ANY OIL. Stop running until all this can be corrected. You may be in for a piston meltdown. One of the best things I ever did was have my injectors serviced. About $25 each.

Have you ever checked the resistance of each pair from the trigger? Have you ever looked at the wires of the trigger? Early OEM units had really crappy wire.

 

[ripcuda]

Thanks for advice Tim75.
See full story details in first post ^^

My triggers ohmed all 3 equally low... 950 ohms... where book says 1100-1300. Based on wires and loom... the triggers are not original. Could this affect only upper rpms?

Plugs were new... and they now have an hours run time... all at low cruising ~3800 rpms... below the perceived problem rpms. I'll report back on their conditions.

I tried pulling one-spark plug boot off (at a time) while cruising at 3800... to see if I could detect a dead cylinder... but after the 2 attempt... I still detected no difference in engine running and ceased trying all 6. Maybe the first 2 I tried were actually dead cylinders?? Seemed unlikely to me... but I do need to test spark at speed. All plugs spark fine when cranking over (not running)

Cheers!

 

[Tim75]

Thanks for advice Tim75.
See full story details in first post ^^

My triggers ohmed all 3 equally low... 950 ohms... where book says 1100-1300. Based on wires and loom... the triggers are not original. Could this affect only upper rpms?

Plugs were new... and they now have an hours run time... all at low cruising ~3800 rpms... below the perceived problem rpms. I'll report back on their conditions.

I tried pulling one-spark plug boot off (at a time) while cruising at 3800... to see if I could detect a dead cylinder... but after the 2 attempt... I still detected no difference in engine running and ceased trying all 6. Maybe the first 2 I tried were actually dead cylinders?? Seemed unlikely to me... but I do need to test spark at speed. All plugs spark fine when cranking over (not running)

Cheers!

According to the service book, the 2 black boxes on top of the engine can be damaged if engine is run without boxes being grounded.

But- since your engine runs, I suspect your boxes are not damaged. According to a local dealer- those boxes cannot be tested. Not sure I believe them. They had to have been tested at the factory. SOMEBODY can test them.

Check all your ground wires. There are several. No green connections allowed.

Continue removing spark plug wires one at a time. Yes, I know what 40,000 volts feels like. Only too well. Or get the spark testers.

There is a black/yellow wire on top, aft of engine. Disconnect and test again. Do you have the dreaded "throttle guardian"?

 

[ripcuda]

More testing results...

Tested TPS... thankfully it is perfectly in spec... from zero throttle to WOT.

Pulled plugs for a read. Some telling signs here. #1 (top-starboard) is not firing... plug still looks new. #2,3,5,6... all look good. #4 (middle-port) is darker/oilier than rest.

Don't #1 & #4 share the same trigger?




I ohm-tested #1 CDM and #2 CDM. #1 CDM is an original part (right in pic). #2 CDM is a newer Quicksilver part (based on sticker - left in pic). Per specs in the service manual... both test the same (w/i just a couple ohms of each other... diodes working as expected).

I'm still going to swap them on the boat and run somemore... and confirm the non-firing spark plug doesn't follow the CDM.




If non-firing spark plug remains at cylinder #1 after the CDM swaps... I guess that points to the trigger, right?

Cheers!

 

[JohnnyG22]

It could still be a bad plug or plug wire. I've had a band new plug not work.

 

[Shortrun]

If you have a clamp on timing light it will tell you if your plug is firing.

Also, I think you have the same engine as mine, 240hp gen 1. We were able to test the injectors by first moving the ECU computer from its mountings, then pulling back the intake manifold a couple inches. Then triggering the injectors with a 9 volt battery. Might be worth trying?

 

[ripcuda]

If you have a clamp on timing light it will tell you if your plug is firing.

Also, I think you have the same engine as mine, 240hp gen 1. We were able to test the injectors by first moving the ECU computer from its mountings, then pulling back the intake manifold a couple inches. Then triggering the injectors with a 9 volt battery. Might be worth trying?

Good tip about the timing light as a spark checker.

I did test and clean the injectors via a bench rig setup with lift pump sucking injector cleaner & premix concoction into the VST... and the high pressure pump feeding the injectors.... while I pulsed the injectors... ensuring all work and have good spray patterns. I'm confident the injectors are clean and good to go.

Cheers!

 

[Tim75]

If you have a clamp on timing light it will tell you if your plug is firing.

Also, I think you have the same engine as mine, 240hp gen 1. We were able to test the injectors by first moving the ECU computer from its mountings, then pulling back the intake manifold a couple inches. Then triggering the injectors with a 9 volt battery. Might be worth trying?

Spark plug #1 looks like it has never fired at all. Did it have any fuel on it or was it dry? #4 looks like it has been running rich. The others look OK.

Clamp-on timing light is a good simple idea, but if you have a bad plug, there may be voltage for a spark, but no spark.

While you are ohm-ing- check your injectors. Round connector, 5/8 dia., down low, starboard side. There are only 4 wires. One ground and 3 injector wires. 2 inj. fire (spray) at the same time. You are looking for the same numbers across ground and 3 pair. I do not remember the spec. If you try the 9V battery test, be aware that you are firing 2 inj., not just one. If you can't actually see the inj. spray, the good inj. could hide the problem with the bad inj.

 

[ripcuda]

Finally got back to wrenching on my Merc. (Took last weekend to install an ac mini-split... crazy hot here in the PNW).

I had a bad regulator and was only running on one during above described sea trials. I knew the regulator was bad because it instantly blew its fuse. I replaced both regulators with a pair of new, cheapie, fleabay regulators. I decided to try and help them last by adding a heat sink to there metal-case backsides. I ordered some 60mm x 60mm x 10mm heat sinks... which fit ideal on the reg case backside. I then had to get +10mm longer bolts also. I used some heat sinking compound (zinc oxide) and bolted them both on.

Both seem to be working fine... no blown fuses... a solid 14.5v at the battery at idle... and both are equally warm to the touch.





Cheers!

 

[ripcuda]

After the new regulators... I got back to the business of diag'ing my apparently not-firing #1 cylinder (clean spark plug... see previous pic).

I swapped the #1 coil (on the don't-look-like-its-firing) with the #2 coil (looks good)... and put a new spark plug in #1 also for good measure. Using the good tip for the timing light... I checked that all 6 cylinders were appropriately flashing the timing light at idle.

The engine still ran the same... had no power above 4k rpms. Stopped and pulled #1 and #2 plugs... both wet... not a good read since we'd only just idled around.

Decided to try the timing light while we took the engine up to ~ 4k to see if we were dropping a cylinder. BINGO! Cylinders #1 and #4 both drop just above idle (~2k). All other cylinders seemed okay up to ~4k... except maybe #6... it was flaky... but only dropped near 4k... not lower like cylinders #1 and #4.

So from all this... we're looking at a likely bad trigger right? Since #1 and #4 share the same trigger?

I previously ohmed the trigger and all three values were ~940 ohms... below the spec of 1100-1300 ohms. But all cylinders fire fine at idle. Starts and idles great.

Cheers!

 

[Shortrun]

Under the fly wheel there are 6 wires from the 3 trigger coils. As Tim said to me (and others) the insulation on these wires crack and are the source of many problems. Doing intermittent things when they shake with engine vibration.
These 6 wires go down to the igniters but on a fuel injected engine they pass through the control module (to supply the EFI ECU with timing) So the Control module is also a possible source of your problem.

Look at the 6 wires first, I think. Maybe do your ohm test again, this time shake the 6 wires while testing to see if the ohms reading jumps around. Which would be a bad thing.

edit
look at my post #18 (wiring i made for my engine in the middle area you can see the Control module)
2000 240 M2 will not start

 

[906merc]

Ripcuda, iam having the same issues with #1 & #4. Mine starts and runs great until I shut it off, then when I restart and start to get on plane I drop cylinders 1 & 4 (plugs are fouled). Something is getting heat soaked when I shut it off. The weird thing is it runs great as long as I don't shut it off.

 

[ripcuda]

I have a new CDI-made trigger assembly coming. I'll report back my findings when I get it installed. Hoping this will fix my dropped spark issue.

Cheers!

 

[Tim75]

I have a new CDI-made trigger assembly coming. I'll report back my findings when I get it installed. Hoping this will fix my dropped spark issue.

Cheers!

The CDI trigger- I have been using a CDI trigger for about a year. When I installed it, the instructions spec'd the resistance as 800-1050 ohms. Lower than OEM spec.
Can you check the resistance while the engine is hot?

I have had this happen to me. The issue was actually bad spark plugs. 2 had internal shorts. Plenty of volts to spark, but shorted to ground.

 

[906merc]

I have a CDI trigger on order also. When testing my old trigger I get 1235 ohms across 2&5, 3&6 and 1170 ohms across 1&4.

 

[ripcuda]

The CDI trigger- I have been using a CDI trigger for about a year. When I installed it, the instructions spec'd the resistance as 800-1050 ohms. Lower than OEM spec.
Can you check the resistance while the engine is hot?

I have had this happen to me. The issue was actually bad spark plugs. 2 had internal shorts. Plenty of volts to spark, but shorted to ground.

Interesting on the lower ohm spec for the CDI trigger. My existing triggers all ohm around ~940 to 950 ohms... below the 1100-1300 ohm spec in the service manual.

While using a timing light... clamped around the spark plug wire... it stops flashing on cylinders #1 and #4 above idle ~2000 rpms. This implies no spark at all from the coil pack, right? A bad spark plug would just ground the spark and not let it jump across the gap. I also did put in some known good plugs in the bad cylinders to no effect. So... I'm hoping it's the trigger assembly.

I'll do a cold and hot ohm test on the triggers when I get them.

Cheers!

 

[Tim75]

Interesting on the lower ohm spec for the CDI trigger. My existing triggers all ohm around ~940 to 950 ohms... below the 1100-1300 ohm spec in the service manual.

While using a timing light... clamped around the spark plug wire... it stops flashing on cylinders #1 and #4 above idle ~2000 rpms. This implies no spark at all from the coil pack, right? A bad spark plug would just ground the spark and not let it jump across the gap. I also did put in some known good plugs in the bad cylinders to no effect. So... I'm hoping it's the trigger assembly.

I'll do a cold and hot ohm test on the triggers when I get them.

Cheers!

If you have an aftermarket trigger, it may test different ohms than Merc spec. Most important is that the 3 pairs test the same.

 

[Shortrun]

While using a timing light... clamped around the spark plug wire... it stops flashing on cylinders #1 and #4 above idle ~2000 rpms. This implies no spark at all from the coil pack, right? A bad spark plug would just ground the spark and not let it jump across the gap.

Just FYI
Sometimes a spark plug will fail and the timing light will flash but there won't be a spark.
I just had this happen to me on a older 65 hp Merc. outboard.

 

[ripcuda]

Back wrenching on the B.O.A.T. Got the new CDI trigger assembly and flywheel puller. Pulled the flywheel... it is in good condition, no magnet issues, clean and nice.



I pulled the existing trigger assembly. Huh... wouldn't you know it... it is also a CDI trigger assembly (same part number on the sticker. Before I put this new one on, I want to test them. The CDI info sheet that came with the new one does say the CDI triggers ohm less than the OEMs... 800-1050 ohms resistance (verses OEM 1100-1400 ohms). I'm starting to doubt if my existing trigger is bad.

After testing both... my existing one is like only 10 ohms less in each trigger... but well within the CDI specs.

Perhaps it has an issue when at operating temps. So I baked it at 200 deg F... which would be hot temps on the Merc. Ohms do increase with temps.

-----------------70degF---130degF--200degF
Pur <> Blu-------968------1096------1102
Wht <> Red-----953------1093------1102
Brn <> Yel-------961------1098------1108

The brand new one tested w/i 10-15 ohms of each of these too.
So I don't think my existing trigger assembly is the problem... darn.

 

[906merc]

Mines all fixed, ended up being the ignition module box.

 

[ripcuda]

Mines all fixed, ended up being the ignition module box.

Thank you for the update to your similar issue!

I've ordered a DVA for my multimeter so I can test the stator, trigger and CDM's as per the service manuals. I'm hoping to get more clear indication of my issue.

I've suspected my own ignition control module... as it had a broken/missing ground wire on it (and the Rev-limiter box too) when I got my boat. I repaired the ground wire and the engine starts and idles great... but that may not be the full story.

I'll update as more testing gets done.
Cheers!

 

[ripcuda]

So I bought a bunch of parts... and am sorta to the point of just firing the parts cannon at this engine... but I'd like to learn it better. The ignition system with all the CDM's and how their circuitry goes through each other... and shared triggers... and control modules... oh my!

I've been working through the static and cranking testing steps while I'm on the trailer. I bought a DVA and the CDM test harness. Time to start cranking.

CDM resistance/diode tests: All my CDMs passed the diodes checks. And all had acceptable resistance across ground-to-trigger (pin A <> C). Similarly... all tested acceptable from ground-to-spark plug cap. Sadly, 3 of the 6 used CDMs I bought (I bought a whole outboard coil plate part-out)... had no continuity from ground pin to spark plug cap.

Spark gap test: All my CDM were able to create a spark to jump the 11mm gap (which is huge!)... a couple weaker than others (I'm going to swap them out with some good used ones I bought).

Stator output test (cranking): spec is 160-320 volts. CDMs #1-#3 = 217v and CDMs #4-#6 = 256v.

Trigger Input test (cranking): spec is 0.2-2.0 volts. CDM #1=0.80, #2=0.86, #3=0.80, #4=0.66, #5=0.72, #6=0.66.

Next up with be back in the water... more voltage tests running at 2500rpms. Manual says it's not necessary if it passed all the cranking voltage tests... but I'm curious. And my spark drop happened around 2400rpms. These readings all seem to indicate my stator charging coils are good... and my trigger is good... which leaves the control module (got a new-used one of those too). So next time on the water, hopefully I can finally solve/cure my 4k rpm max... (due to 2 cylinders dropping spark).

Cheers!

 

[ripcuda]

Finally got back on the lake for some testing. (Bad smoke and scorching temps push me to other projects.)

Engine is still running the same. Starts great, idles fine. As soon as you throttle up... around ~2400 you can hear it start missing and running rough. Then it maxes out around 4k and it just can't power any higher (running on 4 cylinders).

Using a timing light... I can see I'm still dropping cylinders #1 and #4 around that 2400 rpms.

I used the CDM test harness again to get 2500 rpm voltages. Where at cranking speed... all voltages were reading proper. At 2500 rpms, the trigger voltage (spec is 2-8 volts) was dropping like a rock way below 2, then below 1... this happened only on #1 and #4 cylinders. Which makes sense... they share the same trigger. While the good cylinder #2, held a steady 2-3 volts.

I did try another CDM and spark plugs in cylinder #1, no difference.

I even tried another Ignition Control Module, no difference.

Thankfully, the stator voltage at the CDM was good for every CDM tested.

So, time for a new trigger assembly. The one I have is a CDI trigger unit... and ohm tested fine... and voltage tested fine when cranking... but failed at speed.

Cheers!

 

[ripcuda]

Update: Fixed it (new trigger assembly)!

I finally got a new trigger assembly in. The CDI trigger assembly shown a few posts up turned out to be bad. One of its triggers (of 3 on it) must have had a break in the coil... there was no continuity across that trigger. Curious... both my existing failed trigger and the first new trigger I bought was CDI brand... which is supposed to be good... yet both were bad in some way.

I ended up buying the common, cheaper 'Jetunit' brand trigger assembly. It looked of no worse quality than the CDI unit it replaced. And it works!


My engine now can rev past 4k. Sweet! I am seeing ~5300 rpms at 45 mph. I think there is still some rpms left on the table on the top end. I believe my throttle linkage isn't opening fully at WOT. I plan to investigate this further... but honestly... the boat is running good... planes out good... sounds good running on all cylinders and 45mph is plenty fast enough for me.

I did perform an extended WOT run and plug chop (killing engine while at WOT to inspect spark plug color/condition). All 6 plugs look perfect and even... so I'm very happy with that.

Now time to enjoy the boat and see what other curious issue arise with more, prolonged usage.

Cheers!