MERCURY LASER EFI - What's the bare minimum needed to run?

[pcrussell50]

3368777[/URL]]To work right you'll need a fuel regulator, tps, map, and temp sensor.

Sorry for the hijack, but map sensor and not maf sensor? Does that mean that this system does not use a mass airflow sensor? A lot of early efi cars used lookup tables instead of direct measurement of air flow.

-Peter

[OnPad]

Correct, only map.

[Smalltownbassin]

I still havent had time for a water test with the rain we are getting but did have a break long enough for a muff run with the 200PM ecu. Still starts by just looking at the key lol but like several archived threads ive read, its surging at idle. Possibly a MAP issue based on those threads. Im also getting pretty warm on 1 & 3 yet plugs are all wet so its not a lack of fuel. Entire ignition is new and firing correctly so im doubtful of it being the culprit. Anyone have any input on this before i go digging again? Motor runs great on carbs BTW.

[OnPad]

How many rpm are you surging?
How much variation in temp, and is this different than it was with carbs?

Likely culprit.
Map.
Vacuum leak.

Less likely.
Plugged injectors.
Screens in fuel system.
Intermittent temp sensor.

[Smalltownbassin]

Fluctuates 200rpm about 30 seconds into idling and doesnt stop. Port temps are 125-130 & starboard is about 150-160 at 1 & 3 but 5 is in the same range as the port side. Normal with carbs back on it. I dug pretty deep into some archived threads (thanks for keeping them around Greg!) and my issues are very similar to the problems described in a 280 surging thread. No change in idle when i move the TPS. Havent yanked the MAP hose yet while running to see what happens but will when i bolt it all back up. I got a little frustrated and slapped the carbs back on just to get some water time when the rain breaks but plan on continuing the venture before spring. My hopes were to get the system functioning before springing for a Brucato. Seems link im short on tools to effectively troubleshoot some of these things like a vacuum gage & fuel pressure gage for the basics. How will the ecu react to unplugging the head temp? Would it default to cold or warm? Or does it have a default without a temp input?

[Smalltownbassin]

Oh and i thoroughly cleaned all the injector screens along with the entire laser system before putting it together. I tested the injector solenoids with a DC power supply and they all trigger fine but not officially flow tested. All check valves in the bleed system are functioning so not loading the reeds. I didnt see any concerning amounts of fuel moving through the bleed lines either. Less than carbs actually. IDK man. Anyone have time to talk me through some basics on the phone this weekend if i bolt it all back on?

[OnPad]

I would like to be able to help you, but your knowledge already eclipses mine.
You might be able to put a syringe on the map hose and gently pull a little vacuum, for testing?

[Baker343]

I'm not an expert on EFI stuff by any means but what bleed lines are you referring to.
I've been watching this post because I will be converting my stock PM EFI to the external fuel pump and accessories.
I've never done this swap and I'm still reading post and looking for pictures to build confidence.

[Smalltownbassin]

I would like to be able to help you, but your knowledge already eclipses mine.
You might be able to put a syringe on the map hose and gently pull a little vacuum, for testing?

Haha i dont know about all that but thanks for the confidence. I either have some pages missing from my manual or i thumbed right past these in my haste. Thanks OnPad! This gives me some basic paths to verify a few things that seem to be the likely issue.

[Smalltownbassin]

I'm not an expert on EFI stuff by any means but what bleed lines are you referring to.
I've been watching this post because I will be converting my stock PM EFI to the external fuel pump and accessories.
I've never done this swap and I'm still reading post and looking for pictures to build confidence.

The bleed lines im talking about are your check valves on the port and starboard side of the front half. In stock form they all tie together and return the pooled fuel in the reeds to the VST tank for recirculation. A carbie sends them to the cylinders. With a VST delete, im not entirely sure what you do with them. Maybe send a few to the crank mains for added lube?

[PanRonnie]

Page 414

[OnPad]

Smalltown, I went back to post 20.
You say it's getting hot on 2 cylinders, just on the efi setup. That kinda sounds like dirty injectors.
Did it surge with the 150 ecu also?

Question for any smarties out there.
Is it possible to use a map from auto, for replacement of defective unit in ecu? Or is unit buried in potting material?

[PanRonnie]

Yep it,s completly potted i managed to remove the cover by heating it and digging out the potting pain in the ass
Is the surging on the hose? You can only really check if it has the back pressure of water

[Smalltownbassin]

Smalltown, I went back to post 20.
You say it's getting hot on 2 cylinders, just on the efi setup. That kinda sounds like dirty injectors.
Did it surge with the 150 ecu also?

Question for any smarties out there.
Is it possible to use a map from auto, for replacement of defective unit in ecu? Or is unit buried in potting material?

Yeah it did a little bit with 150ecu but nowhere near as bad. It really seemed like the 150 computer just couldnt give the old girl the amount of fuel needed even at just idle. This is the block that thrived on 86 mains in WH-46 bodies. Plugs are wet with fuel though too. This is why ive always been a fan of carbs haha! I dont know enough about EFI to feel good about running it. Too many pieces to fail and injectors love to fail lean opposed to carbs that usually fail rich in comparison. One is catastrophic and the other is just a nuisance. Me being a non racer and just an enthusiast of these old black motors, carbs give me all i could ever ask for. I just really wanted to play with injecting the "frankenbeast" to see how it compared and then decide on buying a brucato as a permanent setup if it made sense compared to the carb performance. At this point i cant afford to rebuild another block lol!

[Smalltownbassin]

Yep it,s completly potted i managed to remove the cover by heating it and digging out the potting pain in the ass
Is the surging on the hose? You can only really check if it has the back pressure of water

Yeah ive only tested it on muffs. Since im an hour from water in all directions i like to get my ducks in a row before making the haul. Ive owned a 200FF EFI before and didnt have a single issue like this but it also was a stock setup. The way this block sounds at idle with efi is similar to drag car if that makes sense. Doesnt seem right to me for a 2stroke outboard.