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Old 05-23-2012, 10:34 PM
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André André is offline
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94 TBI 350 injector cutting under load.

Hey guys!
Boat run great for 4-5 passes through the course then bog around 1600-1800 rpm.
Being a TBI,i can clearly see the passenger side injector completely cutting out and starting back to inject when i pull back the throttle.
I checked visually the wiring and connectors and decided to swap the right and left injectors connectors.The trouble followed the connector and around the same rpms,the driver side injector stopped working,coming back on as i pulled back on the throttle.
Idle is fine.Fuel pressure,lines,pick up and filter are fine.
If the wiring or connection of the injector wasn't good,i think it would bug at idle too but it's injecting fine at idle and instantly stop injecting when it happens.
Any ideas and help is welcome on what to check next.Will double check the wiring and connections tomorrow morning first thing(I took the A.M. off to check this out.Priorities first!The boat,then work!)
T.I.A.
André
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Old 05-23-2012, 10:48 PM
jmhjgh jmhjgh is offline
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I do not have an answer for you, but mine is doing the same thing. It will start surging at about 3000 rpm and you can see the injectors cutting out. My engine runs perfect up to 3000 rpm. I had access to a marine scan tool and everything looks good and with no engine codes.

Have you tried spraying a can of starter fluid or similar down the throat while it is happening? If it gets better, it would point to a fuel problem. On mine, the aerosol did not change the behavior. I was going to check the rubber exhaust hoses to make sure they were not collapsing on the inside, but it is strangely repeatable w or w/o load.
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Old 05-23-2012, 10:51 PM
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j.mccreight@hotmail.com j.mccreight@hotmail.com is offline
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Quote:
Originally Posted by André View Post
Hey guys!
Boat run great for 4-5 passes through the course then bog around 1600-1800 rpm.
Being a TBI,i can clearly see the passenger side injector completely cutting out and starting back to inject when i pull back the throttle.
I checked visually the wiring and connectors and decided to swap the right and left injectors connectors.The trouble followed the connector and around the same rpms,the driver side injector stopped working,coming back on as i pulled back on the throttle.
Idle is fine.Fuel pressure,lines,pick up and filter are fine.
If the wiring or connection of the injector wasn't good,i think it would bug at idle too but it's injecting fine at idle and instantly stop injecting when it happens.
Any ideas and help is welcome on what to check next.Will double check the wiring and connections tomorrow morning first thing(I took the A.M. off to check this out.Priorities first!The boat,then work!)
T.I.A.
André
heres a tbi diag wiring diagram
Attached Images
File Type: pdf MEFI1 MEFI2 TBI Diagnostics.pdf (393.7 KB, 1174 views)
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1989 MasterCraft TriStar 190 SE

Last edited by j.mccreight@hotmail.com; 05-23-2012 at 10:58 PM.
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Old 05-23-2012, 10:56 PM
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I had a similar problem but mine was during idle. It would surge up and down after being used 25+ minutes. Mine ended being one of the injector drivers on the computer board. My computer would need to be replaced if both drivers were bad but the computer was set up to run a 4 barrel and I only have a 2 barrel, so the dealer combined my two injectors on one driver. Been working now for over a year. If it does it again, its a new computer....
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Old 05-23-2012, 11:02 PM
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Quote:
Originally Posted by j.mccreight@hotmail.com View Post
So one injector works properly in either location? I think you alrerady found the problem, you swapped injectors and the problem followed to the other side so you know the wiring is good on both sides so no need to check that, all you need in a new injector, they can fail in numerous ways ...
Sorry,something can get lost in translation when i talk technical stuff.
I swapped the connectors not the injectors themselves.The problem followed the connector.
The passenger side that was cutting at first was now running good and the driver side injector was now cutting out completely around 1800 rpms.
Clear as mud?
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Old 05-23-2012, 11:09 PM
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Quote:
Originally Posted by André View Post
Sorry,something can get lost in translation when i talk technical stuff.
I swapped the connectors not the injectors themselves.The problem followed the connector.
The passenger side that was cutting at first was now running good and the driver side injector was now cutting out completely around 1800 rpms.
Clear as mud?
Mine did the same thing, followed the connection at the computer. Sounds like a driver in the computer. If you, or your mechanic, can combine the two injectors, it should work for you.
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1994 MasterCraft ProStar 205
275 HP 350 Chevy Indmar
Monster Tower & PerfectPass

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"In my many years I have come to a conclusion that one useless man is a shame, two is a law firm and three or more is a congress." - John Adams
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  #7  
Old 05-23-2012, 11:09 PM
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j.mccreight@hotmail.com j.mccreight@hotmail.com is offline
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I misread your post originally, thats why i did the edit thing, i agree with double d its prolly in the ecm you are going to need to hook up a dvom on those pins for the injectors and see if it is losing the ground signal when the boat acts up. it might a little difficult as the ecm is pulsing the ground to fire the injector, but if the injector stops squirting all together then it should not be there, i gave you a diagram for your diag.
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Last edited by j.mccreight@hotmail.com; 05-23-2012 at 11:12 PM.
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  #8  
Old 05-23-2012, 11:13 PM
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Quote:
Originally Posted by Double D View Post
I had a similar problem but mine was during idle. It would surge up and down after being used 25+ minutes. Mine ended being one of the injector drivers on the computer board. My computer would need to be replaced if both drivers were bad but the computer was set up to run a 4 barrel and I only have a 2 barrel, so the dealer combined my two injectors on one driver. Been working now for over a year. If it does it again, its a new computer....
Interresting.I was thinking something similar tonite if it turns out to be the ECM.(Yes,i'm a hacker and cheap!)Any ideas how he did that? Just jumped the wires together at the injectors?
Thanks for the help and ideas guys!
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Old 05-23-2012, 11:16 PM
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JimN JimN is offline
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Quote:
Originally Posted by André View Post
Hey guys!
Boat run great for 4-5 passes through the course then bog around 1600-1800 rpm.
Being a TBI,i can clearly see the passenger side injector completely cutting out and starting back to inject when i pull back the throttle.
I checked visually the wiring and connectors and decided to swap the right and left injectors connectors.The trouble followed the connector and around the same rpms,the driver side injector stopped working,coming back on as i pulled back on the throttle.
Idle is fine.Fuel pressure,lines,pick up and filter are fine.
If the wiring or connection of the injector wasn't good,i think it would bug at idle too but it's injecting fine at idle and instantly stop injecting when it happens.
Any ideas and help is welcome on what to check next.Will double check the wiring and connections tomorrow morning first thing(I took the A.M. off to check this out.Priorities first!The boat,then work!)
T.I.A.
André
Does it only do this when you try to accelerate hard, or can you increase throttle slowly and get it to rev higher?

Unplug the TPS and see if this changes. It will be sluggish and you may see a code/trouble light but go ahead and rev it. If it seems to be OK, check the TPS with a multi-meter set for continuity. If you see the meter react suddenly as you move the throttle, it would seem that the TPS has a problem.
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  #10  
Old 05-23-2012, 11:18 PM
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yes all you need to do is to connect both signal wires from the ecm, but the hard part is knowing which driver in the ecm is bad
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