Injectors - External Leaks

[Contsi]

87' TSi - Had this issue a couple of years ago, found used stock injectors here that ran perfectly.

The car came out of winter hibernation and injectors are leaking. I did a lot or reading here; does not seem to be anywhere to get stock injectors, if so, please let me know, if not, what is the best option.

Thank you for any help

[Keoni1113]

I am in somewhat the same boat. I'm having this bucking issue from my 87 Starion when I get to about 2500rpm. From info and help from others on this forum it may be secondary injector. Switched them out with an 89 conquest and had same issue until learning the 87 may have different injector flow rates then later models

[mikec]

US spec 87-88-89 "wideobdy" cars with intercoolers used the same injectors.

 

The FAQ has a listing of the various injectors used on various Mitsu vehicles. The list includes the "letter code" which is the best way to identify what injector - correct or not - is actually installed on a car. If you look closely at the injectors you'll see a faint stamping just under the plastic band - a number+letter combination. The letter is the key, the numbers don't have any known meaning.

 

On US-spec StarQuests, you'll find basically find 4 different injectors based on production date & intercooled or not:

* the 1983 models had very unique injectors - they look nothing like the injectors for other model years, have their own wires (instead of using a connector), etc. And they fit only the 1983 style throttle body I believe.

 

* 84 to 86 model year cars used medium flow rate injectors, 850cc or something in that ballpark. They have a black plastic band. Letter code is H or J.

 

* 87-later intercooled cars (all US spec models I believe) came with the lower flowing "primary" injector (580cc ballpark) letter code L with a black plastic band, and the higher flowing "secondary" injector (1080cc ballpark) letter code M and a blue or green plastic band.

 

The other letters fit Galants and other Mitsu engined cars and won't work in a stock StarQuest. They'll physically fit into the throttle body... but have totally incorrect flow rates and the StarQuest ECU doesn't learn/adapt much unlike more modern ECUs so the engine won't run very well with incorrect injector flow rates.

 

Note that the 87-later Mitsu factory service manuals use the terms "small" and "large" for the injectors, not primary and secondary. Small/large refer to the flow rates... not the physical injector size as all 84-later injectors are physically the same size. Only the size of the spray tip opening varies - that's what determines the flow rate. The parts list uses "front" and "rear" for the injectors. Front=primary=small

 

mike c.

[Contsi]

US spec 87-88-89 "wideobdy" cars with intercoolers used the same injectors.

 

The FAQ has a listing of the various injectors used on various Mitsu vehicles. The list includes the "letter code" which is the best way to identify what injector - correct or not - is actually installed on a car. If you look closely at the injectors you'll see a faint stamping just under the plastic band - a number+letter combination. The letter is the key, the numbers don't have any known meaning.

 

On US-spec StarQuests, you'll find basically find 4 different injectors based on production date & intercooled or not:

* the 1983 models had very unique injectors - they look nothing like the injectors for other model years, have their own wires (instead of using a connector), etc. And they fit only the 1983 style throttle body I believe.

 

* 84 to 86 model year cars used medium flow rate injectors, 850cc or something in that ballpark. They have a black plastic band. Letter code is H or J.

 

* 87-later intercooled cars (all US spec models I believe) came with the lower flowing "primary" injector (580cc ballpark) letter code L with a black plastic band, and the higher flowing "secondary" injector (1080cc ballpark) letter code M and a blue or green plastic band.

 

The other letters fit Galants and other Mitsu engined cars and won't work in a stock StarQuest. They'll physically fit into the throttle body... but have totally incorrect flow rates and the StarQuest ECU doesn't learn/adapt much unlike more modern ECUs so the engine won't run very well with incorrect injector flow rates.

 

Note that the 87-later Mitsu factory service manuals use the terms "small" and "large" for the injectors, not primary and secondary. Small/large refer to the flow rates... not the physical injector size as all 84-later injectors are physically the same size. Only the size of the spray tip opening varies - that's what determines the flow rate. The parts list uses "front" and "rear" for the injectors. Front=primary=small

 

mike c.

 

Excellent information Mike.

My car runs perfect with stock injectors, even when leaking.

Can stock injectors be purchased anywhere?

What is the best option for aftermarket? Anything not requiring modification?

Thanks

[mikec]

new stock injectors... very difficult to find. If you get the part numbers from the FAQ or the scanned PDF service manual floating around the internet you might find a dealer willing to order them. Be warned though that Mitsu Japan had been sending the wrong injector for the primary... basically sending H/I/J/K (medium flow) injectors instead of the lower flowing L injector. Those injectors in 87-later cars don't work properly - just too rich. So a good used set is about the only option I'm aware of if you want to stick with Mitsu injectors.

 

Trilogy and a few others sell modified injectrors from a different manufacturer. These can work in StarQuests - some folks have them and love them, others didn't have much luck. These injectors are modified by having their upper portions machined to a smaller diameter to fit the stock StarQuest "injector cover" (i.e. the top of the throttle body assembly) and to take Mitsu-style o-rings... or a modified injector cover (the factory openings for the injectors gets drilled to accept larger diameter injector inlets) is sometimes provided. These injectors are a tad taller than Mitsu injectors too - so longer bolts for the injector cover and some spacer pieces are included. These kits are the only simple "buy it, install it, and just drive" alternative. The thing is... almost all fuel injectors available aftermarket are designed for port fuel injection applications. This means they expect to be mounted in the intake manifold right next to where it bolts to the cylinder head. The injector spray pattern is a narrow cone such that the cone diameter is similar to the diameter of the intake valve so majority of the fuel gets sprayed right into the cylinders - and not along the walls of the intake manifold or cyl head passages. The spray velocity is pretty high too - like the "jet" setting on your garden hose gun. On throttle body systems like StarQuests the injector flow pattern is totally different since spraying a cone downwards from the throttle body mounted cone-style injector would just paint the intake manifold with gas. Little would mix with the airflow. Instead, throttle body injectors spray a nearly flat pattern - almost like spraying sideways from the injectors. The resulting flow pattern looks like an open umbrella. The spray velocity is lower too (since the same amount of gas is spread out over a wide plume instead of being concentrated into a narrow cone) so it's much easier for the airflow to mix with the gas and carry fuel to the cylinders. Since the aftermarket injectors "adapted" to the StarQuest throttle body generally have a cone spray pattern the air + gas mixing is poor at low airflow rates (e.g. engine idling) leading to a lumpy idle. At high power the airflow is strong enough to overpower the cone pattern.

 

There are three main types of failures on StarQuest injectors:

1: the electrical coil goes bad. The ECU can't "fire" the injector and the injector is basically junk.

 

2: the "pintle valve" inside the injector gets gummed up with varnish (caused by old/dirty gas) and sticks. When this happens the injector may be stuck closed --> no fuel flow or it may be stuck such that fuel always flows regardless of the ECU commands --> floods the engine and causes black smoke if you re-start the engine a few minutes after shutting it off (7-11 or Starbucks type of trips) Cleaning the injector with spray carb cleaner and a 9-volt battery (to power the coil, moving the pintle) will often cure this failure type.

 

3: the o-rings inside the injector go bad - like any rubber part they eventually get very hard and fail to seal against the fuel pressure. When this happens you'll have gas OUTSIDE the injector, typically oozing/spraying between the plastic and metal parts. The plastic part of Mitsu injectors is NOT part of the fuel seal... fuel is supposed to remain in the center channel of the injector. When the o-rings fail gas squeezes outside the center channel and fills up the injector body - i.e. where the electric coil is and eventually fuel pressure shoves the gas past the plastic parts and you have an external fuel leak. Nothing you can do to properly fix such injectors either. In theory you could open the injector and replace the o-rings but enough stuff gets damaged trying to open the injector that no company is willing to do this. Not profitable. You have to remove the plastic (by busting it apart) without busting the electrical wires to the coil, then "unbend" the curled metal lip of the round central can-shaped part of the injector (where the coil lives) to free the inlet pipe and the flat metal disk grabbed by the curl. You can't see this disk nor the curl normally because they're covered by the plastic. Then you can lift off the inlet pipe + disk, remove the coil, and see a couple o-rings. Replace them (after chipping out the old ones - they'll act like they are glued to everything), re-curl the metal, and mold new plastic. Easy-peasy? Not hardly.

 

If your car has un-fixable injectors, the options basically boil down to:

1: take your chances on finding a good set of used injectors for sale. Who knows how long they'll last though.

 

2: try the aftermarket ones - with the less than ideal spray pattern. They may be good enough for you - as I noted above many folks have daily driver StarQuests running okay with the aftermarket injectors and others have had bad luck with them.

 

3: jettison the stock throttle body setup and replace it with some kind of port fuel injection: new manifold, new injectors, new fuel computer, etc. Not for the faint of heart and may not be legal in some smog-testing areas. There are no complete "just buy this kit and install it" setups out there to my knowledge.

 

4: Replace failed stock injectors with other Mitsu style throttle body injectors that may have different flow rates (much more choice, much more chance of finding new old-stock injectors) and adjusting the car to work with them: e.g. new fuel computer like the Megasquirt that you can program to work with whatever injectors you use, or some scab-on gizmo that alters the stock airflow sensor to stock ECU data stream to compensate for the different injectors. Not impossible but no simple & direct "buy this, install it, and just drive" solution... everything needs some tuning.

 

Obviously #1 and #2 are the easiest options. Injector failures, and the cost of new injectors, airflow sensors, and a few other parts, lead to many StarQuests getting traded in on "easier" cars long ago... or getting junked... or getting engine swaps. Combined with dealer mechanics that often had poor skills with these cars... only dedicated fans of the car keep them!

 

mike c.

[Contsi]

new stock injectors... very difficult to find. If you get the part numbers from the FAQ or the scanned PDF service manual floating around the internet you might find a dealer willing to order them. Be warned though that Mitsu Japan had been sending the wrong injector for the primary... basically sending H/I/J/K (medium flow) injectors instead of the lower flowing L injector. Those injectors in 87-later cars don't work properly - just too rich. So a good used set is about the only option I'm aware of if you want to stick with Mitsu injectors.

 

Trilogy and a few others sell modified injectrors from a different manufacturer. These can work in StarQuests - some folks have them and love them, others didn't have much luck. These injectors are modified by having their upper portions machined to a smaller diameter to fit the stock StarQuest "injector cover" (i.e. the top of the throttle body assembly) and to take Mitsu-style o-rings... or a modified injector cover (the factory openings for the injectors gets drilled to accept larger diameter injector inlets) is sometimes provided. These injectors are a tad taller than Mitsu injectors too - so longer bolts for the injector cover and some spacer pieces are included. These kits are the only simple "buy it, install it, and just drive" alternative. The thing is... almost all fuel injectors available aftermarket are designed for port fuel injection applications. This means they expect to be mounted in the intake manifold right next to where it bolts to the cylinder head. The injector spray pattern is a narrow cone such that the cone diameter is similar to the diameter of the intake valve so majority of the fuel gets sprayed right into the cylinders - and not along the walls of the intake manifold or cyl head passages. The spray velocity is pretty high too - like the "jet" setting on your garden hose gun. On throttle body systems like StarQuests the injector flow pattern is totally different since spraying a cone downwards from the throttle body mounted cone-style injector would just paint the intake manifold with gas. Little would mix with the airflow. Instead, throttle body injectors spray a nearly flat pattern - almost like spraying sideways from the injectors. The resulting flow pattern looks like an open umbrella. The spray velocity is lower too (since the same amount of gas is spread out over a wide plume instead of being concentrated into a narrow cone) so it's much easier for the airflow to mix with the gas and carry fuel to the cylinders. Since the aftermarket injectors "adapted" to the StarQuest throttle body generally have a cone spray pattern the air + gas mixing is poor at low airflow rates (e.g. engine idling) leading to a lumpy idle. At high power the airflow is strong enough to overpower the cone pattern.

 

There are three main types of failures on StarQuest injectors:

1: the electrical coil goes bad. The ECU can't "fire" the injector and the injector is basically junk.

 

2: the "pintle valve" inside the injector gets gummed up with varnish (caused by old/dirty gas) and sticks. When this happens the injector may be stuck closed --> no fuel flow or it may be stuck such that fuel always flows regardless of the ECU commands --> floods the engine and causes black smoke if you re-start the engine a few minutes after shutting it off (7-11 or Starbucks type of trips) Cleaning the injector with spray carb cleaner and a 9-volt battery (to power the coil, moving the pintle) will often cure this failure type.

 

3: the o-rings inside the injector go bad - like any rubber part they eventually get very hard and fail to seal against the fuel pressure. When this happens you'll have gas OUTSIDE the injector, typically oozing/spraying between the plastic and metal parts. The plastic part of Mitsu injectors is NOT part of the fuel seal... fuel is supposed to remain in the center channel of the injector. When the o-rings fail gas squeezes outside the center channel and fills up the injector body - i.e. where the electric coil is and eventually fuel pressure shoves the gas past the plastic parts and you have an external fuel leak. Nothing you can do to properly fix such injectors either. In theory you could open the injector and replace the o-rings but enough stuff gets damaged trying to open the injector that no company is willing to do this. Not profitable. You have to remove the plastic (by busting it apart) without busting the electrical wires to the coil, then "unbend" the curled metal lip of the round central can-shaped part of the injector (where the coil lives) to free the inlet pipe and the flat metal disk grabbed by the curl. You can't see this disk nor the curl normally because they're covered by the plastic. Then you can lift off the inlet pipe + disk, remove the coil, and see a couple o-rings. Replace them (after chipping out the old ones - they'll act like they are glued to everything), re-curl the metal, and mold new plastic. Easy-peasy? Not hardly.

 

If your car has un-fixable injectors, the options basically boil down to:

1: take your chances on finding a good set of used injectors for sale. Who knows how long they'll last though.

 

2: try the aftermarket ones - with the less than ideal spray pattern. They may be good enough for you - as I noted above many folks have daily driver StarQuests running okay with the aftermarket injectors and others have had bad luck with them.

 

3: jettison the stock throttle body setup and replace it with some kind of port fuel injection: new manifold, new injectors, new fuel computer, etc. Not for the faint of heart and may not be legal in some smog-testing areas. There are no complete "just buy this kit and install it" setups out there to my knowledge.

 

4: Replace failed stock injectors with other Mitsu style throttle body injectors that may have different flow rates (much more choice, much more chance of finding new old-stock injectors) and adjusting the car to work with them: e.g. new fuel computer like the Megasquirt that you can program to work with whatever injectors you use, or some scab-on gizmo that alters the stock airflow sensor to stock ECU data stream to compensate for the different injectors. Not impossible but no simple & direct "buy this, install it, and just drive" solution... everything needs some tuning.

 

Obviously #1 and #2 are the easiest options. Injector failures, and the cost of new injectors, airflow sensors, and a few other parts, lead to many StarQuests getting traded in on "easier" cars long ago... or getting junked... or getting engine swaps. Combined with dealer mechanics that often had poor skills with these cars... only dedicated fans of the car keep them!

 

mike c.

Thank you so much Mike, you are the best at this. I have to weight my options.