Overfuelling on my 4.3 TBI

Overfuelling on my 4.3 TBI

Postby Chop [OP] » February 22nd 2018, 8:23pm

Ok guys- overfuelling problem...
'87 4.3 TBI hasn't been on the road for 10 years, I've replaced: plugs, leads, dizzy, oil pressure sensor, temp sensor (driver's side head) MAP sensor, PCV valve and all vacuum pipes connected as per diagram.
She's bollocking that much fuel through her I've had to turn the dizzy almost 50/60 degrees anticlockwise from #1 at TDC on compression stroke to get her to run. After running for a while she seemed to settle down a bit ( like it came off of choke?) But then after turning her off to connect up timing light she wouldn't start again. Eventually after keep pulling the fuel pump fuse out to try and balance her into running and idling, it seems according to the light she was 40 degrees anticlockwise, which we turned slowly clockwise and got to 15 degrees before she just cut out.
My mechanic thinks that we're not going to be able to set the timing properly until the fuelling is right as we're just compensating for it.
Has anybody else had this problem and am i missing something obvious??
Also on disconnecting the tan and black wire the manual says about, she just won't run at all.
Any constructive help is welcomed here! Thanks in advance :chevy:
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Extra Info: 4.3 TBI Shorty CS

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Re: Overfuelling on my 4.3 TBI

Postby AstroWill » February 22nd 2018, 9:16pm

Getting a nice spray from the injectors? What is your fuel pressure? Ensure plug wires are correct. IAC working properly?

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Re: Overfuelling on my 4.3 TBI

Postby Chop [OP] » February 22nd 2018, 10:20pm

AstroWill wrote:Getting a nice spray from the injectors? What is your fuel pressure? Ensure plug wires are correct. IAC working properly?

No the injector spray isn't brilliant to be fair, only when it's full on spray
Plug wires are fine, IAC seems fine as it was idling nicely before choking itself out
Unaware of fuel pressure, what should it be?
Original Poster [OP]
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Re: Overfuelling on my 4.3 TBI

Postby AstroWill » February 22nd 2018, 10:38pm

9-14 running, but I shoot for the higher side. Injector spray should be a nice cone shape.

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Re: Overfuelling on my 4.3 TBI

Postby Big_kid » February 23rd 2018, 3:07am

I found it easier to see the injector spray pattern when it's illuminated by a timing light.
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Re: Overfuelling on my 4.3 TBI

Postby Chop [OP] » February 23rd 2018, 8:22am

AstroWill wrote:9-14 running, but I shoot for the higher side. Injector spray should be a nice cone shape.

It is cone shaped when it's pissing through, but when it had settled it was a bit messier. Does mine have a fuel pressure regulator? If so where's it located?
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Re: Overfuelling on my 4.3 TBI

Postby markmitchmarkmitch is online! » February 23rd 2018, 1:36pm

On the injector pod in the back right behind the two injectors its kind of rocked in under the top . I would normally have a pic to show but I am on a small tablet on vacation. Google GM TBI fuel pressure regulator you may get a picture. If the regulator is bad it could be the problem.
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Re: Overfuelling on my 4.3 TBI

Postby Chop [OP] » February 23rd 2018, 6:35pm

markmitch wrote:On the injector pod in the back right behind the two injectors its kind of rocked in under the top . I would normally have a pic to show but I am on a small tablet on vacation. Google GM TBI fuel pressure regulator you may get a picture. If the regulator is bad it could be the problem.


Thanks mate I've been researching it and can see where it is now so that will be on my to do list
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Re: Overfuelling on my 4.3 TBI

Postby AstroWill » February 23rd 2018, 7:42pm

Get the entire rebuild kit for the TBI while you are in there, it's cheap and once you start pulling things apart...

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