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FUEL INJECTOR

Fuel Injectors dirty

Porsche Cars North America (PCNA) recommends that you use a product containing the Chevron Techron additive to keep injectors clean and fully functional. If you notice hard starting, rough idle, or weak acceleration you may want to try running a bottle of this additive to your next fill up of gas.

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From: DON ISTOOK istook@

Subject: Injector seal kit part #

Injector seal kit PN# for all 944(S)/924S/944 turbo/84-up 911/85-up 928 is 944.110.901.00 (Bosch # 1 287 010 704). This kit includes the "hat" for the injector tip.

They "list" for $3.30 from Porsche. Hope this helps all that need to reseal their injectors. Don Istook

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From: weinec@rpi.edu (Christopher Weinert)

>Subject: noise on top of engine

>I've just encountered a rather interesting new noise on my engine, and I can't >seem to locate where it's coming from. As soon as I start it, it has a high >pitched squeal which seems to be coming from the top of the engine above #3 >cylinder. It goes away momentarily when I open the throttle a (etc.)

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I have a similar car, and had a similar problem, though it was more of a gradual thing than an abrupt condition. After trying variations on the above, I replaced my injector seals (the ones down inthe manifold get fairly warm and dry out over time). This got rid of a lot of strange noises (this was at about 205Kmiles),

and removed a stumble the car exhibited when cold. It is also a cheap fix (watch out for the ball in the fitting at the end of the fuel rail if you opt to drain excess fuel fromt the rail during this procedure; it will roll plenty far if you let it get away).

A while later I noticed that the noise was back, though the stumble was not. After thinking about it for a while (ie- much procrastination) I bought a new intake gasket and popped off the intake. Sure enough, there was a section of gasket which had failed (!) on the upper edge of the #1 port. I replaced the

gasket (at about 225K miles) and was doing very well until my girlfriend had a little oversteer problem last weekend and totaled the poor thing.

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From: debequem@

Subject: 944 Turbo Injectors

Has any one replaced their injector O rings and plastic cap on the business end of the injector?

My 89 Turbo has a set of orange caps that pop off, followed by the O-ring, and finally, a fiber washer.

The replacement kit has a thicker gray plastic washer, same O ring, and a thicker (same diameter, but taller), yellow plastic cap. This cap looks like a small hat with a hole at the top.

When the replacement kit is assembled, the injector nozzle no longer sits flush with the end of the yellow plastic cap, but is recessed by about 1/16" (1.6 mm).

The original parts, when assembled, had the nozzle flush with the top of the orange cap.

We have double checked with the parts department and they claim the kit (Porsche part number 944 110 901 00) is the correct kit for all 944s (Turbo as well). Any ideas? Marv, debequem@

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From: "Moore, Roger" rog@

Subject: Fuel injector replacement

I'm preparing to change my injectors (& pressure valve & damper) and wanted to ask a couple of questions. First, would it be advisable to use rebuilt injectors? They are alot cheaper (NOPI has them for $26.00 each compared to 64.00 for new) but I'll pay for new ones if "rebuilding" means "washing" or something. What does rebuilding constitute with regards to injectors? ROG ---> '84 944

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Subject: Subject: 951 Fuel Injection Mystery Problems

The intermittent power loss under acceleration sounds like a classic fuel pump problem. I've experienced a similar problem on a 911. Alternatively, a faulty DME relay can cause the same sort of symptoms. I had a frind who experienced this at the track under really hard acceleration, again in a 911, but the systems should be roughly comparable. Terry

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To: Timothy.Radsick@dlr.de

Subject: Re: 951 Fuel Injection Mystery Problems

Timothy.Radsick@dlr.de writes:

The engine was making a clicking sound (about 3times the speed of a heartbeat) >at idle. When I push the throttle, the sound accelerated with it. But when I >let go and let the engine get back to idle, it stops until the engine gets back >to idle speed.

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This is also normal and kind of a neat way to prove that your throttle switch is working. When the DME sees a closed throttle switch and engine speed above 1200 rpm, it knows deceleration is in progress and shuts off the injectors. The instant the throttle switch opens or engine speed drops below 1200 rpm, injection resumes. This is a fuel saving and emissions function that many performance chip makers remove from their programs. It causes that jerky feeling when you’re trying to drive slowly around parking lots.

Subject: Re: Question on injectors and injector drivers, 9/13/99L

From: "Martin Taylor" martin.taylor@.nz

From: TurboTim timer1@

>I have a question for those tech heads. Does each injector have its own >injector driver in the DME?

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No, there are only two driver circuits, the injectors are fired in pairs.

Pairs are 1 and 2 then 3 and 4.

>If so does each injector wiring harness have its own ground going into the DME?

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No again, the injectors are all fed +12v from the DME relay / ignition switch circuit, the DME switches the other side of the two circuits to ground.

Subject: Re: 951 Injectors, 9/14/99L

From: hensonator@

"BTW, you can often diagnose a failed FPR by unplugging one of the injectors. If the car only runs with an injector wire unplugged then yours is almost certainly failed."

Yes, it should always be able to run on 3 cylinders but I was talking about it ONLY being able to run on 3 .. as in if you have all 4 hooked up it won't run but if you disconnect 1 it will. Then it's the FPR. See? Cool. I've heard of at least 2 techs discovering this problem in the last 3 months and discussing it on the IATN forum.

Subject: Re: 951 Injectors, 9/14/99L

From: John Anderson blackbox@san.

I've run 17-18psi with stock injectors on my 951 I have a Garrett T60 Turbo. No problem with delivery yet...infact, I am running on the rich side. I feel the stock injectors are good for much more than we give them credit for.

Subject: Re: Injector cleaning, 9/16/99L

From: "TonyG" toeknee@

I would recommend RC Engineering in Torrance CA.

They are what almost all racers use. These guys have an extremely expensive, fully computerized fuel injection test bench. Nothings done by "eye".

They can clean, rebuild, enlarge, flow balance, change spray patterns, etc. to almost all injectors.

In addition, I had them flow bench my stock 951 injectors and the HR injectors (at the same time) for comparison purposes. The 110K mile stock Bosch injectors flowed almost perfectly and were all within .5% (yep... 1/2%) of each other. These injectors had never been cleaned or serviced. They charge $10 per injector to run multiple flow tests on each injector.

Some of the computer printouts of the flow tests, of both the stock Bosch and the HR Racing injectors can be viewed on my 951 website along with photos of their test bench on the "injection" webpage (look for the drop down box on the bottom of the page that says "additional webpages".

Go to:

Or go directly to the injection page at:



I can honestly say that I was not only impressed, but got a decent "readers digest" version of injector flow theory education while I was there.

Remember to multiply the readings by 2x since our injection systems are batch fire (fire every cylinder revolution).

Subject: Re: do I need to replace this fuel injector? 5/10/00

From: John Wade jwade@

I rebuilt the engine in my '88 944 NA this winter and had the same problem on two of my injectors. The yellow cap in the injector kits did not seem to fit and the instructions said not to remove the red cap, so I called Bosch technical support. They couldn't answer my question and referred it to the Bosch engineers in Germany. After several weeks, they called me and reported that the yellow caps do not fit our injectors (P/N 0280150158). They also said that there is not a replacement cap for our injectors and that the only remedy is to replace the injector. They were very apologetic, but did not offer any other assistance. I bought some used injectors from Ian at Ian's Europarts.

Subject: Cleaning fuel injectors, 6/7/00

From: "Sean Pecor" sean@

I'm trying to zero in on a rich mixture problem that seems to be related to partially clogged or incontinent fuel injector(s). I found a great overall Volvo engine performance and tuning FAQ at that has much that applies to the 944 in regard to fuel system performance. One section covers cleaning fuel injectors and describes one process where an ultrasonic cleaner is used. This intrigued me so I went hunting on-line for benchtop ultrasonic cleaning systems. The best and most economical one I found was the Branson B200 (6.5"x3.5"x2.2" stainless steel tank size). It does 40,000 cycles and has a 5-minute timer. Being the obsessive DIY'er that I am. I ordered the product from a distributor ($110.00) and will have it by Friday. This weekend I'll put it through its paces and let you all know how it performs. Even if it fails at the task I set before it, I'm sure the cleaner will have other uses in the shop.

The link for the Volvo FAQ is:



The link for the Branson product info is:



Subject: Cleaned fuel injectors, 6/11/00

From: "Sean Pecor" sean@

My fuel injector cleaning project was very successful. The goal was to clean each injector in my 85.5 944NA using a Branson B200 ultrasonic benchtop cleaner typically used to clean optical gear and jewelry. Each injector was given an ultrasonic bath in a fuel injector cleaner solution (in my case, Gunk FI cleaner) for 15 minutes. Then, after allowing the injector to cool (they get hot from the 40khz vibrations), I activated the injector and used compressed air to blow small amounts of FI cleaner directly through the nozzle to flush out debris. Worked like a charm! I know I could have had them sent off and professionally cleaned, but for the same cost I've got a cool new cleaning device that will last for years to come.

Afterwards, the engine idle increased to 1100RPM, a 200RPM increase likely due to some lazy mechanic bumping up idle to "fix" a rough running engine. After adjusting idle down to 840RPM, I took it for a quick romp and the results were pretty dramatic. Instead of the vibrations that had rattled my shift lever while cruising at 2700RPM, I enjoyed delicious engine harmonics and a quiet cabin. I also restored power that, as a recent 944 convert, I didn't even know was there (grin). I'm hoping I've also neutralized my rich condition with this project.

As for the Branson B200 benchtop unit, I'd say for $110.00 it is a great buy and I highly recommend it (). There was a considerable amount of ultra fine black debris in the tank after all four injectors had their bath (carbon deposits?). I imagine that I'll find a bunch of uses for it in my shop, not to mention in the home (it cleans jewelry, eyeglass frames, printer heads, etc.).

Subject: Re: WTB: Injector Rebuild Kit, 6/17/00

From: "BCN" bcn@

You checked the dealer? Just picked some up, 944.110.901.00 ~$3.50/injector.

Subject: RE: WTB: Injector Rebuild Kit, 6/17/00

From: Clifton Hipsher clifh@

Pelican Parts has O-Ring and pintel cap kits for $5.10 per injector:



Subject: RE: Injector Rebuild kits, 6/19/00

From: "Laches, Peter C LCDR" LachesPC@EVERETT.NAVY.MIL

I don't think so. I went to Pep Boys and said I needed seals for my injectors. $1.99 per kit. Pulled off the old reddish caps and replaced them (w/powder blue I think) new ones. Couple a months ago, no problems.

Subject: Re: Injector Rebuild kits, 6/20/00

From: Markus Blaszak mblaszak@

I use a Bosch authorized agent to do the rebuilding on injectors for me for my business. He has replacement pintle caps for these injectors and they are from Bosch. Sounds like someone is giving you a story just to sell injectors. I would love to see that letter in writing from Germany saying that the pintle caps are not replaceable!! Bet it doesn't exist.

Subject: Injectors/ setting CO%, 6/22/00

From: Ted Harlan trharlan@

I cleaned out my injectors with an ultrasonic cleaner and some Techron, as another lister had suggested. My idle increased by 500 RPM.

I had to turn some screws to drop it down; it now idles at 850 RPM. And "damn, it's smooooth." And a little quicker. Very glad I did the clean and re-seal job.

My concern is that the CO% is probably way off. Is there a way to set the CO% without special tools? I realize that to set the CO%, one needs only a proper

allen wrench. I guess I mean "set the CO% to the proper level."

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