Engine breaking down at low revs!
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holdenrules
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Engine breaking down at low revs!
Ok i bought a gemi coupe wih the setup already done its got a 2.0 dohc turbo with out the fuel injection gear, now the guy said that he would recomend a dyno tune before giving the motor to much, we go fo a drive in the car and it seems as tough it wont rev past 4500 revs. I have put a new coil , new points and checked the timing. It seems as though the car is running out of fuel and that the carby may need bigger jets but a mechanic said it could be the electrics and they may need upgrading. the fuel pressure is sitting on around 7psi. The car has got a tacho i was just thinking maybe it has a rev limiter on it not to sure would this casue the car to back fire and breakdown when your getting around 4500 revs any of your guys help would be great thanks
Was it originaly an EFI engine?
It sounds to me like its either a restricitive intake or maybe even a restrictve exhaust. With the turbo it would probably be the exhaust.
If it was a limiter of some sort you would feel it holding back in each gear although if it just an unmodified carby version it would not have the electronics on it to have a limiter.
Just some thoughts.
It sounds to me like its either a restricitive intake or maybe even a restrictve exhaust. With the turbo it would probably be the exhaust.
If it was a limiter of some sort you would feel it holding back in each gear although if it just an unmodified carby version it would not have the electronics on it to have a limiter.
Just some thoughts.
Sounds to me like fuel starvation - needs a bigger pump? (Or restrictive lines & filters etc.)
Take her somewhere and run until she cuts. Then turn the ignition off (but not if it locks the steering etc!) and into neutral.
Then pop the bonnet and check the carby bowl for fuel, or - if not visible - maybe a fuel filter if fitted between the pump and the carby.
I suggest stopping the car before performing the last step.
Being a 2L DOHC it would have been EFI. And with points - probably from a 117.
Very unlikely to have a rev limiter (you can check that the only wiring is from points to coil -ve with some take-off to the tacho).
Besides - redline should be over 6000 RPM.
Points should be fine to 6500 RPM or more, and later reluctor type dizzies to 8000 RPM (though an internal ferro-magnetic plate (washer?) tends to crack up at 7500 RPM).
Take her somewhere and run until she cuts. Then turn the ignition off (but not if it locks the steering etc!) and into neutral.
Then pop the bonnet and check the carby bowl for fuel, or - if not visible - maybe a fuel filter if fitted between the pump and the carby.
I suggest stopping the car before performing the last step.
Being a 2L DOHC it would have been EFI. And with points - probably from a 117.
Very unlikely to have a rev limiter (you can check that the only wiring is from points to coil -ve with some take-off to the tacho).
Besides - redline should be over 6000 RPM.
Points should be fine to 6500 RPM or more, and later reluctor type dizzies to 8000 RPM (though an internal ferro-magnetic plate (washer?) tends to crack up at 7500 RPM).
IZU069 - Isuzu means a lot to me.
You say the Fuel pressure is sitting at around 7 PSI Is that throughout the rev range right through to the stumble? If it is then you do not have a pressure problem but you may have a bad float level setting. If the float is to low thenyou could quite well be draining he carby before it can refill. The problemwith this idea is it would not do it at the same revs in each gear, it would drain at higher revs each gear higher you go. I know this is sacrilige here but my sis's VC Brock does the same thing sometimes ad the issue is either the float level is to low (more often than not) or the fuel pump is not pumping efficiently (somtimes).
Is it a mechanical pump or is it an electric? If it is electric do you have a pressure regulator after the fuel inlet s the pressure is kept on the carbies needle and seat or do you have it before the needle and seat?
Give us more info on the makeup of the system so we can see what may be happening
Is it a mechanical pump or is it an electric? If it is electric do you have a pressure regulator after the fuel inlet s the pressure is kept on the carbies needle and seat or do you have it before the needle and seat?
Give us more info on the makeup of the system so we can see what may be happening
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holdenrules
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Thanks for the replies and help, um the car is running a holley blue fuel pump and a pretty big stromberge carby. The car only seems to do it after it goes on boost and seems to be starvin of fuel. I dont have a fuel regulator on it but will have very soon. I might strip the carb down and put a fuel regulator on it and see how it goes. I put a new tacho in not because i thought it had a limiter because it was to big but i havent taken it for a drive yet but will see if the old one did have a limiter. any more info will be great thanks
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Poida
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A Holley blue is a non regulated fuel pump. It needs to have a fuel regulator in line.
I can't imagine you are starving from fuel because of a pump supply problem if that pump is all ok. It seems that the Stromberg is more likely to be the culprit.
If the carby was set up to run a non turbo engine in the first place then it may be starving for fuel when it gets to boost. All you can adjust is the depth the needle sits in relation to the jet. Apart from that you need to use the correct needle profile and the correct jet size for the application. Generally speaking a number 090 jet is about what will be in it from factory but that also depends on what it was originally fitted to. On the carby there will be a model/part number so see if you can spot that and quote it. I'm guessing it will be a 2" CD Stromberg.
The needle will have a small mark on the flat shaft, something like 6H for example and the needle also needs to be correctly seated in the base of the piston when the lock screw is applied. It has to be set at the right depth for the whole thing to function. It could be a simple case of the original builder not knowing the needle needs seating right. Also, the damper may have the wrong viscosity fluid in it. Some vehicles need thin oil or transmission fluid and some use none at all apart from a smear of machine oil to prevent the piston wearing (LC XU1 for instance).
Just so many variables that need to be covered before the problem can be resolved.
I'd suggest have it checked at the same time it's dyno tuned. That should reveal why it suddenly stops building revs. Don't go pushing it or you might end up punching a hole in a piston if it is leaning out.
As for rev limiters, they might be in the form of an odd type of rotor button with a spring loaded rotor tip if there is such a thing. The Ford Lotus engines used one to limit their engines. Have a look to see if the rotor button looks different at all.
I can't imagine you are starving from fuel because of a pump supply problem if that pump is all ok. It seems that the Stromberg is more likely to be the culprit.
If the carby was set up to run a non turbo engine in the first place then it may be starving for fuel when it gets to boost. All you can adjust is the depth the needle sits in relation to the jet. Apart from that you need to use the correct needle profile and the correct jet size for the application. Generally speaking a number 090 jet is about what will be in it from factory but that also depends on what it was originally fitted to. On the carby there will be a model/part number so see if you can spot that and quote it. I'm guessing it will be a 2" CD Stromberg.
The needle will have a small mark on the flat shaft, something like 6H for example and the needle also needs to be correctly seated in the base of the piston when the lock screw is applied. It has to be set at the right depth for the whole thing to function. It could be a simple case of the original builder not knowing the needle needs seating right. Also, the damper may have the wrong viscosity fluid in it. Some vehicles need thin oil or transmission fluid and some use none at all apart from a smear of machine oil to prevent the piston wearing (LC XU1 for instance).
Just so many variables that need to be covered before the problem can be resolved.
I'd suggest have it checked at the same time it's dyno tuned. That should reveal why it suddenly stops building revs. Don't go pushing it or you might end up punching a hole in a piston if it is leaning out.
As for rev limiters, they might be in the form of an odd type of rotor button with a spring loaded rotor tip if there is such a thing. The Ford Lotus engines used one to limit their engines. Have a look to see if the rotor button looks different at all.
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archangel62
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Yeah, I was thinking along the lines of what Poida said - except I don't know half as much 
. I've heard of plenty of problems running turbo blow through carby, because the carby isn't set up correctly, some people even think you can't do it (which of course we know isn't true).
I'd say have it dyno tuned by someone who really knows their carbys, tell them about the problem and have them try re-jetting it or even rebuilding part of it to rectify the problem.
. I've heard of plenty of problems running turbo blow through carby, because the carby isn't set up correctly, some people even think you can't do it (which of course we know isn't true).I'd say have it dyno tuned by someone who really knows their carbys, tell them about the problem and have them try re-jetting it or even rebuilding part of it to rectify the problem.
Twincam needs: surge tank, EFI lines, TPS, recored radiator, hoses, assemble the ECU (50% done).
Could you clarify what type of Stromberg it is that is on the car. If it is a CD Stromberg it should be before the turbo. Yes they can go after the turbo but it is an awful lot of fiddling to set them up right.
CD Strombergs are Constant Depression carbies, this means they require a vacumm (depression) on the engine side to operate properly, if they are setup as a blow though turbo the they do not have a vacumm they will have difficulty sucking the fuel through. Something like a Holley, Rochester Quady, plain Stromberg can be setup relatively easily for a blow through turbo system simply because of their design.
The other thing about a blow through system is in theory a carby that is setup correctly naturally aspirated will when setup properly as a blow through turbo setup be very similar in jeing etc. Why well simply because the carby does not change just because the air pressure does. If anything the power valve setting would be the only thing that requires modification inside the carby. Te other thing that you must do is set up the fuel delivery (ie Pump and regulator) to increas in pressure as the manifold presure increases. To do this you need a rising rate regulator hooked up to recieve turbo pressure. This is not as critical on an EFI engine but is on a carby setup that is blow though.
CD Strombergs are Constant Depression carbies, this means they require a vacumm (depression) on the engine side to operate properly, if they are setup as a blow though turbo the they do not have a vacumm they will have difficulty sucking the fuel through. Something like a Holley, Rochester Quady, plain Stromberg can be setup relatively easily for a blow through turbo system simply because of their design.
The other thing about a blow through system is in theory a carby that is setup correctly naturally aspirated will when setup properly as a blow through turbo setup be very similar in jeing etc. Why well simply because the carby does not change just because the air pressure does. If anything the power valve setting would be the only thing that requires modification inside the carby. Te other thing that you must do is set up the fuel delivery (ie Pump and regulator) to increas in pressure as the manifold presure increases. To do this you need a rising rate regulator hooked up to recieve turbo pressure. This is not as critical on an EFI engine but is on a carby setup that is blow though.