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schoward's Avatar
 
Join Date: Nov 2005
Location: Jersey Shore
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New Injectors - Experiences

I searched and found nothing here related to any break-in period of new injectors, etc. but question...

I recently replaced two more injectors as I did two more injector seals and sleeves. Figured at 36 years old, the originals could be retired. Exact bosch replacements.

I have noticed maybe smoother and stronger idle and seems to pull smoother to redline when I get on it. Don't think I gained any power but don't think I lost any either.

One I think that seems to be happening though -- I run the lambda system and it seems that under light throttle I now feel slightly more 'hitching'/dithering at certain light throttle speeds and upon application of throttle from light throttle positions which in turn sometimes feels like less throttle response with the brand new injectors. It does seem with the new injectors I can cruise with lighter throttle which I guess is good and when I press throttle down hard and I guess get the enrichment all seems fine.

I have read that injectors sometime need a 'break-in' period but not sure if really true. I popped them in and did not pressure check etc., as I was hoping to get lucky. And I have replaced individual injectors in the past with no issue. I rechecked my mixture and all normal/same as before.

Anyone have similar experience either less response, tightness, break-in etc. associated with brand new Bosch fuel injectors (under 100 miles on them)? Worst case I guess I can swap back to old ones to check.

Thanks.

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Scott
1981 911SC Targa - Platinum Metallic
Old 07-24-2017, 07:58 AM
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Send your old ones to mr injector for rehab? For $18/each, he cleans and replaces filter and seals. You also get a printout of flow test - before and after. Doesn't hurt to have a spare set.
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Old 07-24-2017, 08:03 AM
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Not the mechanical CIS fuel injectors.......

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Originally Posted by mepstein View Post
Send your old ones to mr injector for rehab? For $18/each, he cleans and replaces filter and seals. You also get a printout of flow test - before and after. Doesn't hurt to have a spare set.

Mark,

The CIS fuel injectors are sealed and you can not remove or replace the filter/s without cutting or destroying these injectors. Maybe you were referring to the EFI (?). And there are no seals to replace. Have you actually seen the internal parts of these CIS mechanical injectors? Keep us posted.

Tony
Old 07-24-2017, 08:58 AM
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Or just keep a few bottles of Techron in your garage. If injectors work fine and do not leak, why replace them? Techron clears them up in just a few miles and cost $8.00 a bottle.
Old 07-24-2017, 08:59 AM
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Quote:
Originally Posted by boyt911sc View Post
Mark,

The CIS fuel injectors are sealed and you can not remove or replace the filter/s without cutting or destroying these injectors. Maybe you were referring to the EFI (?). And there are no seals to replace. Have you actually seen the internal parts of these CIS mechanical injectors? Keep us posted.

Tony
Your right, my mistake. I was thinking 3.2 but obviously didn't read the post in full.
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Old 07-24-2017, 11:31 AM
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Just as an update, like when I replaced the injectors on the 1-2-3 side, again doing the other 4-5-6 side made the engine run and feel, I don't know, 'tight' when running and accelerating immediately after replacement.

Could have been in my mind, but just like first side, after 2-3 drives (not particularly hard and not long duration) and seems things went back to normal and I have no complaints.

Perhaps the new fuel injectors do need a little 'break-in...'. After all they are a little simple mechanical device. Could be in my mind but all good.
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1981 911SC Targa - Platinum Metallic
Old 09-28-2017, 01:07 PM
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I replaced all of the fuel injectors in my 82 SC about 6 months ago. Smoother idle but thats the only part that I could really feel. I was having an issue with very difficult hot starting after sitting for about 25 minutes with high ambient temps. The CIS gauges confirmed it wasn't the check valve or fuel distributor. Hot and cold pressures were correct but the car still was stubborn to start. When it did there was a "miss" for about 5 seconds and then all was well.

Anyway, new injectors were the last thing I expected to cure my hot start issue but they did. Must have been leaking down.
Old 09-28-2017, 01:18 PM
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Quote:
Originally Posted by niner11 View Post
I replaced all of the fuel injectors in my 82 SC about 6 months ago. Smoother idle but thats the only part that I could really feel. I was having an issue with very difficult hot starting after sitting for about 25 minutes with high ambient temps. The CIS gauges confirmed it wasn't the check valve or fuel distributor. Hot and cold pressures were correct but the car still was stubborn to start. When it did there was a "miss" for about 5 seconds and then all was well.

Anyway, new injectors were the last thing I expected to cure my hot start issue but they did. Must have been leaking down.
The symptoms you describe are usually a failing accumulator. How long did the system hold pressure after turning off?

Old 09-29-2017, 04:59 AM
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