Intermittent Idle - Fuel Delivery Part 1

Up to this point, I've attacked issues with vacuum leaks, spark plugs wires, and deteriorating electrical wiring in an effort to restore a smooth engine idle.

In the case of the Endless Corrado, the very last of the four items which may affect smooth engine operation is the fuel delivery.

With 176k miles on the clock, The Endless Corrado project hasn't had any major upgrades or maintenance to the fuel delivery outside of gasoline treatment and routine fuel filter changes.

So the fuel injectors themselves and associated components are highly suspect. It was time for a refresh in the fuel delivery area.

Years ago I purchased a BBM Fuel rail. It was inexpensive at the time because BBM had decided to discontinue manufacturing this item due to lack of demand. However since then, BBM has renewed production of this item due to increase in demand probably because of renewed interest in these older Digifant cars.

Originally I had opted to NOT install BBM item simply because the OEM plastic fuel rail had a fuel inlet that was not accounted for on the BBM rail. In addition, the plastic rail had an outlet at the opposite end which accommodated the Idle after-run switch. If I were to use the BBM rail, then I would need to account for these two attachments. And I would have to reorient the direction of fuel lines in the engine bay.

It then became apparent at this point in the project to simply replace the injectors and to implement the BBM fuel rail. Up to this point, the billet aluminum fuel rail served only as a curiosity(Conversation starter) sitting on my desk. The workmanship and industrial appearance of the piece is impressive.

So I began shopping for replacement parts. As luck would have it--I found a fantastic deal on Bosch replacement fuel injectors. GermanAutoParts was selling sets (4) of the Green top Bosch fuel injectors for $65 each. That's roughly half of the suggested retail price for new Bosch injectors. I am aware there are other alternatives from other cars. Some have used Mustang Fuel injectors. I've also heard of other GM automobile injectors. To me, this introduces other unnecessary complications into the mix. What other issues will non-spec injectors introduce?  There is also the alternative of using rebuilt/recalibrated injectors which are less expensive-- about $285 per set of four.
While searching, I inquired on a few of the popular open forums on possible sources and was told that Corrado injectors can be replaced for $25 each. I never ever found such claims to be true. Many open forum claims are unsubstantiated so I took that claim with a generous amount of skepticism. The Germanautoparts price for brand new Bosch direct replacements was the most logical choice. Furthermore, new injectors are already fitted with fresh new O-rings so that is one less task I will undertake in replacing these parts.

It is good practice when servicing the fuel injectors to also replace the nylon seats in the intake manifold.  These are inexpensive costing roughly $1 each. I could simply reuse the originals but with so many miles the originals may be cracked causing vacuum leaks.

I can also replace the steel clips which secure the injectors to the fuel rail. But I don't think that's really necessary unless they are broken. The originals can be reused if I remove them carefully. Nothing really breaks down or deteriorates with the clips.

To start, I disconnected the battery. With fuel present, we don't want any unwanted ignition potential anywhere near our work area. Then I disconnect the fuel supply hoses on the passenger side of the engine bay.

To access the injectors, one has to remove the Idle Stabilizer valve, any brackets up near the intake manifold, vacuum lines, and the valve cover. This allows ample room for your hands and any necessary tools. From here I can now clearly see the fuel rail, fuel pressure regulator, and the wiring harness.

With all of that out of the way, you should be able to now see the fuel rail and the tops of the injectors. The wiring harness is encased in the plastic heat shield directly behind the fuel rail.

To remove the fuel rail, first remove the fuel lines at both ends of the rail. The after-run idle switch is on the drivers side of the rail. Residual fuel pressure will be relieved once you disconnect the lines and will spill fuel therefore be prepared. I keep lots of shop towels and a fire extinguisher close by-just in case. It helps to practice clean work habits because any spilled fuel is a fire hazard and any dirt or grease can foul the intake or fuel delivery.

The fuel inlet port near the Fuel Pressure regulator

Then remove the fuel pressure regulator on the passenger side of the rail. The two allen bolts can then be removed and then pull the square fuel injector clips. The tops of the injectors have an O-ring which is a pressure fit into the rail. Simply lift up on the rail and those should release. The Fuel Injector harness may have some zip ties and may need to be removed. You may also have to reach in and unclip each of the injector connectors--one from each injector. Once you lift the rail, some of the injectors may also remain attached and lift out of the intake manifold. It is dirty in this area so be careful to not allow any dirt to enter into the injector holes.

Close up of original injectors

The square clips can simply be pulled upwards to release. I used a flat head screwdriver. You'll have to reach your hands in from behind the rail to reach the connectors for each individual wiring harness connector. Squeeze the clips and then pull. This is a hard to reach area so some acrobatics will be necessary. 

Once the fuel rail was removed, I was now able to visually inspect the wiring harness. I've been told this needs to be closely examined because of the extreme temperatures in the area enveloped by the Intake runners. Sure enough, the wires were brittle and there was lots of exposed copper. I was afraid that if I pull on the wires, they would come apart. 

With the injectors out, I can now access the nylon seats of the injectors. This requires a 10mm hex driver. I was fortunate that three of them came out with no hassle. However, the number 3 cylinder stripped. Most have told me they were unsuccessful removing any of the seats. I miss the old CIS or Motronic motors which has a nice solid brass injector seat. Much easier to work with. Some have suggested using a heat gun on that area of the manifold to assist in removal but most said it was futile.
One guy posted that he chiseled it out! I'd be afraid of the debris and dirt that would inevitably be introduced into the intake.

I made a decision after trial fitting the new injector and seals--to simply leave the old nylon seat in place  and forget about it. If I have problems with vacuum, I may have to return to this injector seat.

It was educational to compare the original part to the replacement. So visually see how much wear & tear these components experience is enlightening.

I'm glad I'm freshing this area of the engine. It is one less thing to worry about. Next post will cover reinstallation of the fuel rail and the new injectors.