[rustech]

A couple weeks ago, I noticed cylinder 4 was running a bit lean. I decided to send in the old injectors and change plugs since they were do again. Just thought I would share my results.



Injector type: Sat. 15.5 Ohm

Test pressure: 43 PSI

Test pulse: 6.0 MS

Injector make: Bosch

Gravity Weight: 0.75



Injector 1 2 3 4



Before: 72.9 71.1 68.6 71.4 Difference: 6.3%

Spray Pattern: OK OK N/G OK

Reverse Cycle: Dirty Dirty Dirty Dirty



After: 75.9 75.2 75.9 75.9 Difference: 1.0%

Spray Pattern: OK OK OK OK

Leakage Test: Good Good Good Good



All injectors within specification after cleaning.





I'm very happy with the difference. Acceleration is much smoother all the way to redline, and since that spray pattern on that injector 3 is fixed, I will no longer be running a bit lean in that 4th cylinder. I figure it's good for about an 8 horspower gain (or should I say re-gain) or so. I can definately feel the difference. It was well worth the money, and highly recommended.

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[Anchorman]

What was the total turnaround time, from the time you sent the injectors out until you had them back to be reinstalled? I'd like to have this work done, but can't lose the use of the car for very long

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[rustech]

Since this is only my weekend car, I didn't expedite the shipping. I sent them out on Monday of last week (May 23) and only received them yesterday (Friday June 3). I sent them Priority mail, and they sent them back UPS Ground ($13). Their turnaround time was only 1-2 days to do the work. If you are willing to pay for expedited shipping both ways, you could get a turnaround as fast as 3-4 business days total. Unfortunately, they only send UPS for the return trip.

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[Anchorman]

Thanks. I think what'll I'll do is pull and send the injectors the day I leave for a two-week vacation at the end of August, during which the 968 will not need to be used at all. The injectors should be at my door when I return, and I'll reinstall and start cruising happily.

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[968gene]

I missed the who/where on where you sent the injectors...also, have you considered a de-carb of the head?

Thanks

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[Anchorman]

Good question. I'm betting the answer - as I've been assuming - is Marren.

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[Cloud9...68]

Rustech,



What a timely post! I just sent my injectors to Marren today. I'm glad you're happy with the results. It really looks like the cleaning made a significant difference in terms of flow. I have a few questions for you:



- What type of symptoms was your car displaying before that prompted you to have your injectors cleaned? Mine has a pretty pronounced hesitation/loss of power, particularly at WOT, along with a stumble pulling away from rest. I've tried/ruled out a lot of stuff, so I'm hoping the injector clean/blueprint will do the trick.



- How did you know one of your cylinders was running lean?



Thanks; I'll let everybody know my results as well.

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[rustech]

It says "Marren Fuel Injection" in the subtitle.



De-carb? What's that?



Cloud, based on my plugs, I could tell one cylinder was running too lean. I didn't want to burn any valves or anything, and so had to have them cleaned. I didn't have any other symptoms, not to say a badly clogged injector (<65 flow) wouldn't cause what you are experiencing. My results confirm my lean condition that I had assumed.

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[Cloud9...68]

Rustech,



Thanks. A couple more simple questions:



- To what did you torque the bolts that hold the fuel rail to the intake manifold?



- Did you you any lubricant (silicone?) on the rubber seals around the injectors where the fit into the fuel rail?

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[rustech]

The bolts I torqued into the intake manifold holding down the fuel rail were by feel; keeping in mind the entire time that I was bolting into aluminum. Probably just a hair higher than recommended since it is the fuel rail and all.



I used silicon on all the o-rings. I cleaned the manifold holes and fuel rail holes with q-tips, and then put a thin coating of silicon there as well. Assemble the injectors to the fuel rail first, then line everything up, and press it into place, applying centered pressure over each injector evenly. Since the o-rings are not silicon, there is no harm of deteriorating them with silicon spray.

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[Harvey]

Is it usually good idea to get new o-ring seals, etc. when you change the injectors?



Harvey

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[rustech]

Absolutely, I would never install them without doing so. Marren does this for you when you send them in.

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[Cloud9...68]

Rustech,



I should be getting my injectors back from Marren before the end of this week. One more question, and I'm not sure how you'll be able to give a definitive answer, but here goes. The 19 mm nut attaching the fuel rail to the line was understandably very tight. How did you know how much to tighten it when you put it back on? Obviously, many people have sent their injectors out for cleaning in the last couple of years, so it can't be too much of an issue, but of course if the nut isn't tight enough, I run the risk of a fuel leak in a very bad place, but too tight, and I risk stripping the thread. Seeing as I'm scheduled to take the car out for my first DE the last weekend of June, I really don't want to have that happen. Any tightening tips? Thanks.

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[rustech]

Um, by feel. <img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" />



The hardest part is to get enough torque on them while maintaining constant and full control. Any slips, or side force, and you're asking for trouble. Get both handles of both wrenches relatively close to each other for the final tightening for better stability (and so the force is exerted in opposite directions [towards each other] instead of the same direction to minimize risk of bending). Make sure the wrench on the rail line doesn't move, and bring the handle of the wrench on the fuel line towards the wrench on the rail. When you can't bring them together anyfurther by clenching your hands (or by interlocking your fingers and using your palms) then it's tight enough. It would be very hard to strip the threads, but very easy to bend a line. This answer I've given is subjective at best, but I hope you see my method.

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[Cloud9...68]

Thanks, that's very helpful. I'll be very careful; this close to my DE, i can't afford to repair anything I might break...

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[968gene]

Rus, my decarb question was concerning decarbonizing the head. Your choices are chemical or the old fashion walnut chips route. either way, I'm wondering if you have a build up around the injector port that might be impeding a proper fuel dispersion.

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[rustech]

I didn't notice and dry sort of carb deposits in the area...but I did notice some gunky sort of oil deposits that were very dark that I cleaned out with Qtips.

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[Cloud9...68]

Since I did my injector clean/blueprint through Marren as part of the troubleshooting of my hesitation problem, and the cleaning didn't fix my problem, I wasn't able make any statements as to the effectiveness of the cleaning. However, now that the hesitation is cured (new plug wires did the trick), I can say that the engine now runs phenomenally well. Other that a fair amount of vibration at idle, which I'm sure is due to worn engine mounts (my project for the Fall when it cools off), it runs like a new car. The idle is steadier, pulling away from idle is effortless, and the acceleration is very strong. It even seems to shift more smoothly! The car has 87,500 miles. It's hard to say how much of the improvement is due to the injector cleaning, but I have to believe it's at least partly responsible. Marren was very professional and easy to deal with, and the turnaround was only a couple of days, not counting mailing time. I would highly recommend them. Here are the before & after flow readings on my injectors in cc/min:



Before:

Cylinder



1 2 3 4

Test #



1 69.1 70.6 72.2 71.4

2 68.4 69.9 72.2 71.4

3 68.4 69.9 72.2 70.6



Avg 68.6 70.1 72.2 71.1

St dev 0.361 0.404 0 0.462

Average flow of all four injectors = 70.5

Injecter-to-injector st dev = 1.53

% diff among injectors ((range/mean)*100 = 5.2%



After:

Cylinder



1 2 3 4

Test #



1 74.4 75.9 74.4 75.2

2 74.4 75.9 74.4 75.2

3 74.4 75.9 74.4 75.2



Avg 74.4 75.9 74.4 75.2

St dev 0 0 0 0

Average flow of all four injectors = 75.0

Injecter-to-injector st dev = 0.723

% diff among injectors ((range/mean)*100 = 2.0%



So, Marren's work significantly increased the average flow of the injectors, while cutting the standard deviation among them by half.

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[Cloud9...68]

Whoops, the formatting of my tables didn't end up as I had typed them, but hopefully the results are clear enough...

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