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Thread: Carb vs EFI ?

  1. #31
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    I switched the ECM from the A30 to an A8. They do interchange. Motor runs exactly the same. ECM doesn't seem to be the problem. I pulled apart the EFI fuel system. I took the top off the VST with the fuel pump. It could not be any cleaner. Took the throttle body off and pulled the reeds out to check them. They look perfect. Scratching my head. I don't know what else there is to test. This first EFI is kicking my ass.

  2. #32
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    Pull the fuel pressure regulator off and check for volume. If that checks out pull the cover off the injectors, and check spray pattern. Just make sure to unhook plug wires from plugs, and ground, or you will have a runaway.

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  4. #33
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    Quote Originally Posted by LakeFever View Post
    Starting is easier but still a little tricky when cold because I deleted all the black box helpers. With just switch boxes it’s still prone to stalling when cold.
    a little trick thats done ta help with that is makin' tha start controlled with tha "push tha key ta squirt" for a cold motor...... same as a carb motor.

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  6. #34
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    While I am waiting for a new reed plate gasket, I think I am going to make a test harness to test the injectors. I have the entire system off the motor. I should be able to bench test them by just filling the VST and jumping the pump. It just circulates the fuel through the fuel rail and back to the VST. Then jump the injectors one wire at a time. Each wire fires two injectors. Maybe not all the injectors are firing. The VST was very clean, so I doubt the injectors are clogged. But I may fill the VST with straight seafoam and run that through them on the bench to clean them. I can't think of anything else to try.

  7. #35
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    There's a screen between the regulator, and schrader valve that might need cleaned also.

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  9. #36
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    I think I just had my Eureka moment!!! I changed or tested everything on this motor by the book except the damn detonation module. I just unplugged it. I didn't ground the black/white wire from the ECM. On motors without the detonation module that wire is grounded or goes to the shift switch. On models with the shift switch, the switch breaks the connection on that wire when the motor is in neutral, and grounds that wire when the motor is in gear. If I am not mistaken, when that switch goes bad, the motor runs fine in neutral but won't rev up under load. Just like the problem I am having. That has to be the problem. I really hope so.

  10. #37
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    Quote Originally Posted by tlwjkw View Post
    a little trick thats done ta help with that is makin' tha start controlled with tha "push tha key ta squirt" for a cold motor...... same as a carb motor.

    This motor starts and idols perfectly even when ice cold out. Even after switching it to switch boxes with all the crap removed. No throttle advance needed at all. Cranks for about 3 seconds. Pops once. kicks the starter. Click the key and it starts and idols smooth. Revs right up if you hit the throttle. Restarts every time with just a click.

  11. #38
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    that was for LakeFever....

    jus $hit can tha det module.. not needed anyway........ ground tha gray or gray/white coming from tha ecu...

  12. #39
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    While I have this thing apart, I decided to do a basic static fuel injector test. Giant fail. Some of the injectors don't have a spray pattern. They just shoot a stream of gas like a hose. I guess I should have them cleaned and flow tested.



  13. #40
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    EFI is great when it works. Carbs are more reliable but you have to know how to use them.

  14. #41
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    I tested the fuel injection system from that blown up and corroded motor I took apart. When I took apart the VST, it was filled with dried up orange fuel sludge. I cleaned it out and tested the fuel pump. It's dead shorted. Just sparks when I jump it. So I used my good VST to test the rest of the injector system. From the looks of the VST I figured the injectors would be all clogged up. Go figure, 5 out of 6 look perfect. Spray patterns all look equal with a nice foggy looking spray. The last injector, #6, did not spray at all. I disconnected the power, and I let it sit until the next night. When I checked the next day, I activated the injectors without activating the pump. The injectors sprayed a nice spray pattern for around 5 seconds before fading out. There is no leak down at all. I am going to use these 5 injectors plus one of the good flowing injectors from the first set. I found a place near me that specializes in servicing fuel injectors. According to their website they will do a full service on mercury outboard injectors. They replace all essential components, such as O-rings, pintle caps, spacers and filters for $22.50 each. That is less than I can buy the parts for. Plus, they do a bunch of tests I cannot do. They supposedly pulse test them from 600rpm to 10,000 rpm. cycling through pulse widths from 3ms to 12ms. That way when I put it all back together, if I still have a problem, I can be sure its not the injectors. But I am pretty sure this will fix the problem.

  15. #42
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    I have to change the intake gasket, so I had to take the reeds off. While I was doing that, I noticed how much casting flash was left in the middle of the intake tract. It has to disturb the airflow. I figure I want to do some mild porting on this motor and making power is as much about getting air in as it is out. So, while I had it apart, I took off the flack and sanded it smooth. I didn't make it bigger, I just made it smooth. I don't know how much of a difference it will make. But it won't hurt
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  16. #43
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    I just got back from the injector place. One of my injectors is bad. After cleaning it twice it still flows about 20% less than the other 5. I dropped off 3 more injectors. I will use the best 6. I sure am glad I had them professionally flow tested. On the bench they all looked good to me. I would have had 1 lean cylinder.

  17. #44
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    I got my injectors back. They are all now perfect. The first 6 I brought him had 1 bad injector, #6 and all but one really needed cleaning. #2 injector flowed the same before and after cleaning. The other 3 I brought him were all perfect before and after cleaning. 9 injectors cleaned. 8 flow matched perfectly. $180 total.

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  18. #45
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    Quote Originally Posted by Jim Speros View Post
    I've had both too. Both run great when cared for. As they get older a carb is less expensive and easier to maintain. Carbs are also easier to troubleshoot.
    Quote Originally Posted by tlwjkw View Post
    simple solution, change 'em ta switch box stuff................. get rid of all tha extra junk.

    carbs less problems that come with age... easier ta diagnose problems.. usually cheaper ta maintain..
    efi more convenient (user friendly) till it develops a problem..
    performance limited (production efi) modified efi (hi performance ecu's and such not included)......... jmo.
    These were my instincts on the matter too. And I'm pretty comfortable with the non-OBD, Bosch EFI automotive systems that look a whole bunch like the Mercury EFI systems. For that reason, and the the fact I only get about 30-50 hours a year out of my carb 2.4/200, I'm not looking to replace it. Of course, if I had an EFI V6, I'm pretty sure I'd be comfortable enough keeping up with it. Just not going to spend any of life's precious time, looking for one at the right price.

    -Peter
    "padded wonder"
    __________
    the wet:
    18’ Bahner bow rider, 2.4/200 like this one: https://images.offerup.com/p7x0VYOCm...8704f88eb6.jpg
    Hydrostream Viper, 140 v4 crossflow, some Raker props
    16' Baja/Tahiti/Sidewinder clone, 135 v4 crossflow
    17' boston whaler alert, 90 merc fourstroke
    13' boston whaler, 40hp yamaha

    the dry:
    2003 bmw ///M5
    1993 mustang/griggs racing road race car
    and a handful of clunkers

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