[T3] Fwd: Engine Backfire

BilDylJ at aol.com BilDylJ at aol.com
Wed Jul 18 07:40:05 PDT 2012


 

 
Thanks Jim
I appreciate the help.
My engine ran good for about 4 yr's. I had to leave it outside
(covered} for about 2 mo. and it wouldn't start after. I had it checked  by 
2 { Certified } VW mechanic's they got  it running but it has been 
backfiring on the left side 3 & 4 cylinders ever since. They can't  stop it 
from backfiring. I thought maybe the rubber rings on one of the  injectors 
were leaking air. There are no fuel leaks from the injectors or the  hoses.
The engine starts and run's pretty good But it still starts backfiring  
every time you let off on the throttle and hold it at a steady speed. {approx.  
30 mph}
The engine is in a Trike motorcycle and no one wants to mess with  it.
It must have been set up alright originally it ran good for 4 yr's. 

                                   Thanks Again !
 
 Billy D



 
 
In a message dated 7/16/2012 5:40:58 P.M. Eastern Daylight Time,  
jadney at vwtype3.org writes:

On 16 Jul  2012 at 16:48, BilDylJ at aol.com wrote:

> Can anyone out there tell  me how to change the fuel injectors on a 1972 
> type 3  engine.

I would not suspect injector problems as the source of engine  
backfire, unless you have some non-Bosch injectors there. Non-Bosch  
injectors can usually be easily identified by the fact that they  
don't have the nicely rounded corners around the electrical  
connector.

If you're having problems not related to leaking gas,  I suggest you 
go to the bottom of this message and check the tightness  of all 2 
push on electrical connectors.

There is very seldom any  need to replace all 4 injectors, unless 
you're talking about an engine  that has not run in decades. If the 
problem is gas leaking from failed  original hoses crimped onto the 
injectors, the crimp can be cut off and  that short piece of hose 
replaced. However, you still have to remove the  injectors to do this.

Removing the injectors is a mid level job,  neither easy nor really 
hard, but it is cramped, especially working on  the LHS.

Start on the right. Remove the air cleaner.

Unplug  the electrical connectors from the injectors. Don't pull on 
the wires,  pull on the connector body. (You can feel the body thru 
the rubber  boot.)

Loosen the clamps that attach the multiple port "Tee" to the 2  
injectors.

Rock the Tee back and forth while pulling it out of  the injectors. 
When it comes out gas will spill. Do this outside or with  good 
ventilation. No smoking.

Find a combination of 10 mm socket  and short extension that will let 
you get to the nuts in the center of  the injector mount. Remove both 
nuts and washers.

Pull both  injectors outwards, along with the mounting hardware. Each 
injector will  have a large and small rubber ring. The small ring may 
stay in the  socket when you pull the injector out. The small rings 
are still okay as  long as they are plyable and not broken all the way 
thru. The large  rings are okay as long as they will still fit in the 
phenolic  retainer.

Note that there should be a small metal sleeve surrounding  each 
mounting stud. They may stick inside the phenolic mounting plate.  
They are necessary to keep from breaking the plate.

The phenolic  plate may be broken if the injector has been leaking. If 
this is the  case, you will also need to replace that rubber ring, 
because it will be  swollen too large to fit back in the plate. I just 
swap these and let  the gas slowly evaporate from the rubber and use 
them again in a few  months.

Installation is the reverse of removal. Repeat on the  LHS.

I have all the parts and I can replace the hose ends on the  injectors 
if that's a problem for you.

I have had poor results  with non-Bosch injectors. That's about the 
only time I ever replace an  injector. I have new Bosch injectors, 
too, but I never recommend  replacing injectors unless there's some 
good reason to. They do NOT seem  to wear out, but they sometimes 
develop leaks that can't be fixed. Small  thru leaks can be ignored.

If you are having injector problems, you  should also check that the 
electrical connectors are tight on the  injectors. Bosch made a major 
mistake at some point in their production:  They reduced the thickness 
of the material used to make the injector  pins. This causes huge 
problems with poor connectons there. To fix this,  you must remove 
each pin from it's connector body and very carefully  squeeze it down 
until it is snug on the injector pin. Then snap it back  into the 
connector body. This is actually more work than removing the  
injectors.

-- 
*******************************
Jim Adney,  jadney at vwtype3.org
Madison, Wisconsin,  USA
*******************************

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