Home » Public Forums » GMCnet » [GMCnet] Multi-port Fuel Injection
| [GMCnet] Multi-port Fuel Injection [message #59937] |
Mon, 12 October 2009 23:54  |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
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I spent the afternoon helping change a SB GM engine in a suburban. For
the last month, when the owner tried to start it, sometimes it was very
hard starting. Finally it would not turn over. So he installed a new
starter and battery. It started, but ran rough and developed a knock.
It had a bent rod. One of the injectors was letting all the fuel under
pressure, into a cylinder after shut down. This finally got so bad, it
hydraulicked the cylinder and bent the rod. The piston in that cylinder
is down @ 0.250". I guess a Q-Jet is not such a bad idea after all.
Gordon
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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| Re: [GMCnet] Multi-port Fuel Injection [message #59946 is a reply to message #59937] |
Tue, 13 October 2009 06:34  |
Jim Bounds
Messages: 842
Registered: January 2004
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Gordon,
The problem you described is but one pitfall in direct port injection and actually fuel injection in general when you adapt it to our older motors. Yes, everything today has direct port injection but the manufacturers can spend millions setting up the motors exactly for the car, you do not have this luxury in adapting only one system to one motor. Even getting a tylored chip for the 455, the motors are not all set up the same and years of use have changed characteristics many times so they do not details the same when you get into the fine tuning.
We all better understand the diagnostic tree of a Q-jet, the guy who bent his rod did not recognize the problem he had and ran the motor into the ground. That was because he did not understand what was going on till it was too late. This has happened to me with the direct port FI systems I was messing with.
It really all comes down to what you want and what you are looking for, the first time I saw a direct port fuel injection system on a 455-- I just had to have one and boy did I get it! The guy I got it from did not do his due diligence and never warned anyone on the downside-- we slipped off the hill and bout whiped ourselves out. A well set up carb and an HEI dist do a really good job, they are easy to deal with and in that most folks can set them up, maintain and recognize when there are problems and know what to do about it-- I came full circle and now strongly recommend carbs.-- at least on our GMC.
Of course opinions will vary on this and isn;t it greay we live in America where we can do that.
Sorry for your buddies problem, hey but he knows now!
Jim Bounds
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----- Original Message ----
From: Gordon <wizwing@telus.net>
To: GMCTEMP <gmclist@temp.gmcnet.org>
Sent: Tue, October 13, 2009 12:54:52 AM
Subject: [GMCnet] Multi-port Fuel Injection
I spent the afternoon helping change a SB GM engine in a suburban. For
the last month, when the owner tried to start it, sometimes it was very
hard starting. Finally it would not turn over. So he installed a new
starter and battery. It started, but ran rough and developed a knock.
It had a bent rod. One of the injectors was letting all the fuel under
pressure, into a cylinder after shut down. This finally got so bad, it
hydraulicked the cylinder and bent the rod. The piston in that cylinder
is down @ 0.250". I guess a Q-Jet is not such a bad idea after all.
Gordon
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| Re: [GMCnet] Multi-port Fuel Injection [message #59961 is a reply to message #59937] |
Tue, 13 October 2009 10:09 |
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It sounds like had your friend had a fuel pressure tester, all that could have been avoided. you can get them for about $30 at any auto parts store. they plug into the schraeder valve on the fuel rail and would have picked up on that stuck injector right away. on an EFI motor if you have spark and it doesnt start trubleshoot the fuel system first! would have cost him less then the battery, starter, and now new motor.
I actually find EFI to be overal simpler then the complicated mechanical setups in carbs, with all those little fine parts which can get lost during an overhaul. a fuel injector is basically an on/off selinoid fired by computer control. its the computer aspect which scares most people, but then thats not all that complicated either. with a modern EFI controller like the ones offered by Edelbrock, MSD and Holley, add a wide band O2 sensor controller and the thing pureet much self tunes.
good bosh style injectors have a service life of over 25 years. and only have to be removed for cleaning about every 75k miles. and if thas too much work you can always dump a few cans of FI cleaner in the gas to flush'em out...
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
[Updated on: Tue, 13 October 2009 10:10] Report message to a moderator |
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| Re: [GMCnet] Multi-port Fuel Injection OR TBI [message #59968 is a reply to message #59961] |
Tue, 13 October 2009 11:17 |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
Karma: 0
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Friend's DW had the problem while friend was working out of town. The
fuel pressure tester is how he found the source of the problem. There
was enough fuel in the oil for an "OH,OH"!
I have my fingers crossed that the EBL that Bruce and Ken now have is
the solution to all the stumbling problems that many of the EFI systems
have been suffering. It is certainly the solution to having to re-flash
a chip for every change. If so, a GM throttle body, a $20 727 instead
of a $100 747 and a wideband O2 should equal or better a carb. With ESC
a knock sensor and a speed sensor, one should have a very good system.
Gordon
Shan Rose wrote:
>
> It sounds like had your friend had a fuel pressure tester, all that
> could have been avoided. you can get them for about $30 at any auto
> parts store. they plug into the schraeder valve and would have picked
> up on that stuck injector right away. on an EFI motor if you have
> spark and it doesnt start trubleshoot the fuel system first! would
> have cost him less then the battery, starter, and now new motor.
>
> I actually find EFI to be overal simpler then the complicated
> mechanical setups in carbs, with all those little fine parts which
> can get lost during an overhaul. a fuel injector is basically an
> on/off selinoid fired by computer control. its the computer aspect
> which scares most people, but then thats not all that complicated
> either. with a modern EFI controller like the ones offered by
> Edelbrock, MSD and Holley, add a wide band O2 sensor controller and
> the thing pureet much self tunes.
>
> good bosh style injectors have a service life of over 25 years. and
> only have to be removed for cleaning about every 75k miles. and if
> thas too much work you can always dump a few cans of FI cleaner in
> the gas to flush'em out...
>
>
> _______________________________________________ GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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| Re: [GMCnet] Multi-port Fuel Injection [message #59971 is a reply to message #59937] |
Tue, 13 October 2009 11:53 |
bobby5832708
Messages: 237
Registered: November 2006
Location: Winter Springs FL
Karma: 3
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Senior Member |
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Gordon,
This brought back memories of a similar incident a few years ago with a friends mid-90's Ford Explorer 4.0.
His wife says the Explorer suddenly started losing power and leaves a smokescreen. He checks the oil and finds it WAY overfull. Changes oil and goes for a test drive. Engine idles pretty smooth but has no power and he is fogging out Lake Mary Blvd with what isn't quite an oil smokescreen, but he's not sure what it is. He gets back home and the oil is now several quarts overfull. That's when he calls me.
I figured that the only way for the crankcase on an injected engine to fill up that rapidly was that there must be a stuck injector. With the engine idling and liquid gasoline dripping out of the swiss-cheese exhaust system, I pulled the connectors from each injector one at a time. Turns out the 3 injectors on the right side of the engine were on (open) all the time while the left 3 were working properly. Replacing the ECM (and changing the oil again) fixed it.
I don't know how, but the Explorer didn't catch on fire or suffer any noticeable mechanical damage after being run this way. It ran fine for a long time after that incident. Fuel injection systems usually work fine but they can fail in some pretty "interesting" ways!
GMC content: My GMC's fuel system has the original QJet carb and a Carter electric fuel pump, both of which work fine. No need for an injection system right now.
Bob Heller
2017 Winnebago 29VE
Winter Springs FL
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| Re: [GMCnet] Multi-port Fuel Injection [message #59974 is a reply to message #59971] |
Tue, 13 October 2009 12:10 |
Gary Casey
Messages: 448
Registered: September 2009
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Way back in '79 at Bendix, injectors stuck open were one of the first failure modes we worked on(there were a few Sevilles that hydraulic'd). Then later I developed a system of my own and had to worry about it. There are about 3 ways for it to happen: The injector itself can stick open. Rare, but it can happen - usually they just dribble. The injector driver can fail shorted, leaving the injector on. Some systems are group-fire and more than one injector can stay on (like 3). The only approach for that is to first oversize the drivers to make a failure less likely and then introduce various failure detection schemes - not easy, but many of the modern injector drivers have fault detection built in. Finally, the software can lock up, leaving an injector on. We worked a lot on that, and had multiple layers of fault detection built into the software and then had a hardware watchdog to look a the software. As Bob related below, it's not a good
failure mode - The Explorer must have suffered just the "right" failure, where the injectors would only be on if the engine was turning - that way the engine could keep purging the extra fuel. The unrecoverable problem occurs when the engine stops and an injector keeps dumping fuel.
Gary
________________________________
Gordon,
This brought back memories of a similar incident a few years ago with a friends mid-90's Ford Explorer 4.0.
His wife says the Explorer suddenly started losing power and leaves a smokescreen. He checks the oil and finds it WAY overfull. Changes oil and goes for a test drive. Engine idles pretty smooth but has no power and he is fogging out Lake Mary Blvd with what isn't quite an oil smokescreen, but he's not sure what it is. He gets back home and the oil is now several quarts overfull. That's when he calls me.
I figured that the only way for the crankcase on an injected engine to fill up that rapidly was that there must be a stuck injector. With the engine idling and liquid gasoline dripping out of the swiss-cheese exhaust system, I pulled the connectors from each injector one at a time. Turns out the 3 injectors on the right side of the engine were on (open) all the time while the left 3 were working properly. Replacing the ECM (and changing the oil again) fixed it.
I don't know how, but the Explorer didn't catch on fire or suffer any noticeable mechanical damage after being run this way. It ran fine for a long time after that incident. Fuel injection systems usually work fine but they can fail in some pretty "interesting" ways!
GMC content: My GMC's fuel system has the original QJet carb and a Carter electric fuel pump, both of which work fine. No need for an injection system right now.
--
Bob Heller
1974 X-Canyonlands 26ft
Winter Springs FL
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| Re: [GMCnet] Multi-port Fuel Injection [message #59981 is a reply to message #59937] |
Tue, 13 October 2009 13:36 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
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| Tin Gerbil wrote on Mon, 12 October 2009 21:54 |
I Finally it would not turn over. So he installed a new
starter and battery. It started, but ran rough and developed a knock.
It had a bent rod. One of the injectors was letting all the fuel under
pressure, into a cylinder after shut down. This finally got so bad, it
hydraulicked the cylinder and bent the rod. The piston in that cylinder
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Something we all have to look out for, fuel injection or not. Liquid does not compress. A water leak will also bend a rod if you keep trying to crank it. It either leaks the liquid past the rings and valves until it can turn over, or it bends the rod and then leaks past the rings and valves until it can turn over. In the meantime, what ever liquid is leaking past the rings is now in the oil.
If you try to crank, and it makes a mighty effort, but hits a hard spot (I am not talking about it firing too soon and back kicking because you are using the Think system to time your rig) you need to check the engine out. You are bending stuff and diluting your oil.
Pulled the plugs on a GM V6 one time and it shot water all over the wall of the garage.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] Multi-port Fuel Injection [message #59986 is a reply to message #59981] |
Tue, 13 October 2009 13:57 |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
Karma: 0
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Senior Member |
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George;
Many years ago, I was in a high performance Mustang that had kept making
oil and the Dealership would not do anything about it. The owner
decided to blow it up before the 12,000 mile warranty ran out. He put
it in first and held the throttle to the floor. A loud bang and all 4
of us were laughing in our beer. Huge flame behind us, very, very
comical until we realized we were going uphill and coasting to a stop.
Then the conversation turned to killing the driver, if we survived the
fire. The fire went out before the car came to a stop. "Torchie Bill"
is still alive today.
If your GM is making oil, please find out why?
Gordon
> Tin Gerbil wrote on Mon, 12 October 2009 21:54
>
>> I Finally it would not turn over. So he installed a new
>> starter and battery. It started, but ran rough and developed a knock.
>> It had a bent rod. One of the injectors was letting all the fuel under
>> pressure, into a cylinder after shut down. This finally got so bad, it
>> hydraulicked the cylinder and bent the rod. The piston in that cylinder
>>
>
>
> Something we all have to look out for, fuel injection or not. Liquid does not compress. A water leak will also bend a rod if you keep trying to crank it. It either leaks the liquid past the rings and valves until it can turn over, or it bends the rod and then leaks past the rings and valves until it can turn over. In the meantime, what ever liquid is leaking past the rings is now in the oil.
>
> If you try to crank, and it makes a mighty effort, but hits a hard spot (I am not talking about it firing too soon and back kicking because you are using the Think system to time your rig) you need to check the engine out. You are bending stuff and diluting your oil.
>
> Pulled the plugs on a GM V6 one time and it shot water all over the wall of the garage.
>
>
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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