MAP sensor and vacuum line

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mmarriott2
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Joined: Fri Feb 22, 2013 10:24 am

MAP sensor and vacuum line

Post by mmarriott2 »

Does anybody have a photo of their MAP sensor and vacuum line? My MAP sensor is mounted to a collar between the airfilter can and the TBI unit with no vacuum line attached. The vacuum line goes from port F straight to the PCV line on the vacuum canister. This does not seem correct according to the Howell pics I have managed to find...And no I did not install this set up, The PO could not get it to run correctly. I dont even know if it has the correct MAP sensor, it does not look like the ones Ive seen here.

Id really just like some pics of what this set up is supposed to look like.

1979 Cherokee
360
Howell FI kit

AwesomeJ10
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Re: MAP sensor and vacuum line

Post by AwesomeJ10 »

You talking about a GM howell TBI kit? 7747 ECM?

If so, then the map sensor should be attached to the rear of the TBI via a vacuum line. Nothing else should be sharing the vacuum for the map sensor - it's a dedicated line.

There is usually a green wiring connector with (I believe) 3 wires connected.

FSJ Guy
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Re: MAP sensor and vacuum line

Post by FSJ Guy »

There are two general types of MAP sensors. A "mini" map sensor which is square and the other style I have seen which is (larger) and a rectangle. The rectangular one is generally cheaper. Of course, without them side by side, it's hard to see which is larger, but one is square and the other is a rectangle. Now aren't you glad you paid attention in geometry class? :-p
AFAIK, both are interchangeable, but they do have different connectors that you would have to replace.

X2 on what Black said.
Ethan Brady

http://www.bigscaryjeep.com

Jeepless, but I still have a lots of old parts in my garage!
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jaber
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Re: MAP sensor and vacuum line

Post by jaber »

http://www.binderplanet.com/forums/show ... hp?t=45292

Part way down on the first post there are pics of a TB with all the ports labeled. Its the one on the rear of the TB between the fuel ports.

HTH. :-bd
Jeff

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Topic author
mmarriott2
Posts: 28
Joined: Fri Feb 22, 2013 10:24 am

Re: MAP sensor and vacuum line

Post by mmarriott2 »

Well after learning that the MAP sensor was hooked to nothing, and that its vacuum line was hooked to the PVC line on the canister I decided to download the install instructions for the kit. Wow. None of the lines were routed correctly. In fact he still had the air pump installed and ALL of the unneeded lines were still there, including the air manifolds bolted to the exhaust. So after a few hours, lots of parts and lines removed I had it running like a champ. Just need to replace the EGR now. Thank you everyone for your help.

FSJ Guy
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Re: MAP sensor and vacuum line

Post by FSJ Guy »

Good to hear! The MAP sensor is about the only sensor that is REQUIRED for the TBI to run semi-decently. Most all other sensors can fail and it will run OK in limp home mode.

But the MAP is definitely necessary, IMHO. (And the TPS, too, now that I think about it....)
Ethan Brady

http://www.bigscaryjeep.com

Jeepless, but I still have a lots of old parts in my garage!

AwesomeJ10
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Re: MAP sensor and vacuum line

Post by AwesomeJ10 »

FSJ Guy wrote:(And the TPS, too, now that I think about it....)
yep. I lost a tps a while back and it was causing an erratic, high idle. ran fine though.
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