"Tonto Injectors"
1990 Ford Ranger XLT, Accel Fuel Injector upgrade.  Ford made it hell, but Summit Racing eased the pain.
-Allen Keehall-
Problem: I hate this truck.  It's been nothing but trouble since the day it arrived from the dealer.  But rather than put a final bullet into the POS, I decided to "trouble-shoot" the problem instead.  Tonto often managed to save the Lone Ranger, as I also reasoned  possible for the namesake.

Background: The symptoms seemed rather strange; rough idle, stuttering when running, smokey white then black exhaust after warm-up and an intermittent check engine light.

I checked all the fluids, changed the fuel line filter, checked the fuel for contamination, cleaned out the throttle body, cleaned and re-gapped the plugs, checked the ignition module for "spark" and replaced the air filter.  Then I fixed a vacuum line leak, replaced a faulty PCV valve, and cleaned the mass airflow sensor.  It seemed OK for a week or so then all the symptoms returned. 
I did note that increasing the vacuum leak improved the rough idling (increase in "un-metered" air).

A trip to a mechanic for diagnostics on their antique Ford code reader and he thought it might be the fuel pressure regulator but the pressure was in spec.  So $35 later back to square one, armed with the idea that it was stuck fuel injector(s); explaining the rough idle and fuel-rich exhaust.

Thanks to AutoZone's online repair guides and a
Ford Rosetta stone of fault code, one can read them via the check engine light.  This took a while because there were dozens of stored codes.

The codes indicated either a faulty coolant and throttle body temperature sensor and rich conditions, which is a result of an incorrect combustion mixture.  So a vacuum leak benefited the leaky injectors by allowing a more favorable combustion mixture; reducing rough idle and raising RPM.  That's why fixing the vacuum leak first made things worse.

There's no easy way of inspecting the injectors, but the carbon on the plugs clued that a few were extremely rich.  While researching the injectors it was decided that Summit Racing had the best deal.  Factory new Accel Injectors seemed to be a better alternative than remanufactured or ancient OEM parts.  You can buy a set of 6 injectors for the price of two new OEM Bosch injectors, or 4 remanufactured.
IT'S A NO BRAINER!  Summit Racing made it painless and delivered in three days.

Now some of you would say that was stupid since you would only need two or three at the most, but who cares about another $100 bucks when you're up to your buns in mess and don't want to ever do it again.  Besides, even sending them all out to be professionally cleaned and refurbished would run about $20 bucks each, so an extra C-note buys a new set.  And I did get a really nice free hat!

Disassembly: 
Stuff happens and this is no exception.  A plastic fuel fitting broke for lack of understanding the unusual release mechanism (needs two .020"x0.1" release pins).  And no it wasn't a standard Ford fitting, that tool I own.  There's nothing in the literature on this defunct fitting.

Further disassembly showed that the injectors require a rubber grommet (seat).  They were all in very bad shape.  Thus an insulting trip to the Ford dealership.  The fuel fitting/line was in the neighborhood of $175, the original grommets were $6 each, and made in the UK circa 1985.  Yeah, that sucked.  So the "actually 50 cent" grommets were ordered and I resolved to repair the fuel line.  This required careful disassembly of the steel crimp, machining a mandrel/anvil set, re-profiling the crimp, a brass compression fitting, and re-crimping.  It all worked out great except that
handling brittle woven fiberglass shrouded fuel line is HORRIFIC!  Tape it first and wear gloves too.

While awaiting parts I disassembled the throttle body and fuel rail, re-conditioned and prepped.  That fuel rail is gorgeous.  It's beautifully cast, welded, and machined.  It's a shame it was on a Ford.  But truth be told, it's on an
over-bored Audi engine, since Ford couldn't figure out how to make a good 4-liter V6 at that time.  They attached two in-line catalytic converters to this beast for U.S. emissions.

Assembly:  After cleaning all the removed components, the clean-out of the intake manifold was a huge pain because of the excessive carbon.  I carefully cleaned and polished the injector ports on both the fuel rail and manifold, wire brush the air intakes (brass brush), and regularly vacuum all loose debris.  Use aluminum foil and rubber stoppers or rags to close-off cleaned intakes.

Buy a new gasket preloaded with sealant. 
Do not use any silicone products or sealant.  Siloxanes will ruin your oxygen sensor.  Reverse the disassembly order and use a thin coating of light motor oil on the injector O-rings and on the manifold ports to ease installation.  You may need to re-tape some of the injector lead wires, so neaten the harnesses while doing this.

After assembly clear and reset the computer.  This will place the computer into the learn mode.  Start the engine and let it idle for about 10 minutes.  Then drive the vehicle for about 30 miles under varying conditions, NO FLOOR-BOARDING.  Make it a very leisurely 45 mph max drive with minimal stops.  The last 5 miles can be a high-speed highway run. 
Accelerate smoothly at all times.

Conclusion:  The engine ran great after startup, however the check engine light would come on after a while (lean reading).  The codes inferred a faulty oxygen sensor.  Replacing the sensor solved that problem.  The engine now runs smoothly and has excellent acceleration.

A Few Notes:  A week later I bench tested the old injectors and two were very leaky at nominal pressure.  One was partially leaky but at higher than nominal fuel pressure.  Given the excessive carbonization I made the assumption that perhaps the fuel pressure regulator may be under regulating at times and helped create the
"cascade."

I bought an inexpensive Harbor Freight fuel pressure tester and the readings were well beyond limits.  So I replaced the pressure regulator.  Perhaps the cleaning fluids may have finally pushed the regulator into complete failure (clogged orifice or leaky diaphragm).

It's almost impossible to check an oxygen sensor.  It has a heater and you have to access the computer connector to get to the oxygen sensor leads since the connector is buried near a
HOT exhaust manifold.  That means getting into the computer and checking the oxygen sensor leads.

A Fault Cascade
  • A faulty pressure regulator forces a rich mix, more buildup on the O2 sensor.
  • Oxygen sensor buildup eventually reads lean; the CPU increases the injector dwell time.
  • The increased dwell time creates a further rich mixture and excess carbon buildup.
  • The injectors either stick or clog due to the escalating buildup.
  • A clogged injector forces a richer mix from the CPU by increases dwell time (by now maxed).
  • A sticky injector further carbonizes and clogs the O2 sensor to always read lean.
-10/30/2007-
 Most people spend more time and energy going around problems than in trying to solve them.  -Henry Ford-
After installing fuel rail.
Cleaned Air Intake
Fuel Rail & Air Intake
Injector Port post polishing.
Bosch/Accel Injectors
After installing injectors.
Fuel Fitting and old clip.
New Fuel Fitting.
Fuel Manifold post cleanup.
Accel/Bosh Injectors
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Copyright 2005-2016, Al Keehall-Labs