Doh! No start after cat replacement.

Roc Doc · 03-07-2009, 05:40 PM

In order to shave a few more pounds, I pulled the cat off of my 3.2 and replaced it with a "test pipe". Now it won't start, and the fuse closest to the driver is blown. After replacing it, the car started but quit almost immediately and blew the new fuse. (What's the chances of two bad fuses? [My old college electronics teacher loved that joke.

]) Anyway, the only thing I can think of is the O2 sensor harness my be pinched, I'll have to look at it tomorrow. Could that cause this condition.

BTW, it's an 85 3.2 in a 76 911S, and I've had this combination for almost 20 years.

TIA

craig356 · 03-08-2009, 05:22 AM

Since the only thing you could have messed with in the change from the cat to a test pipe would be the 02 Sensor, process of elimination would make me believe this has to be it. Either a pinched or cut wire, bad connection or somehow debris on the tip of the sensor.....But, I thought all of these things would just make the engine run terrible, not blow a fuse....If there is a wire shorting out from the sensor, I guess this could cause a surge and result in a blow fuse....Should be easy to identify by taking a close look at the sensor wire and connection.

Roc Doc · 03-08-2009, 08:26 AM

Quote:

Originally Posted by craig356

Since the only thing you could have messed with in the change from the cat to a test pipe would be the 02 Sensor, process of elimination would make me believe this has to be it. Either a pinched or cut wire, bad connection or somehow debris on the tip of the sensor.....But, I thought all of these things would just make the engine run terrible, not blow a fuse....If there is a wire shorting out from the sensor, I guess this could cause a surge and result in a blow fuse....Should be easy to identify by taking a close look at the sensor wire and connection.

That's my thinking as well. I'll know in a little while.

rick-l · 03-08-2009, 10:56 AM

I am confused as to which fuse blew.

The OXS heater is unfused and comes directly from the battery through the DME relay. I bet the DME relay will serve as the fuse if that is shorted.

Roc Doc · 03-08-2009, 01:20 PM

Quote:

Originally Posted by rick-l

I am confused as to which fuse blew.

The OXS heater is unfused and comes directly from the battery through the DME relay. I bet the DME relay will serve as the fuse if that is shorted.

The fuse is #18, so that must be where I pulled the power for the DME. It's been a long time since I did this swap

The problem is the O2 sensor itself. The wires are frayed right where they go into the sensor, and they were shorting out. It runs without the O2 connected, so I assume it will just run in open loop with no O2 sensor connected.

Ouch! $160 for a new one.

burgermeister · burgermeister's Garage

You can buy a generic Bosch (or other brand) replacement one for $50. You will have to solder your connector onto the generic replacement. I do not think our host sells the generic replacements. It's the same O2 sensor as the $150 one, it just doesn't come with a connector attached.

Roc Doc · 03-08-2009, 02:33 PM

Quote:

Originally Posted by burgermeister

You can buy a generic Bosch (or other brand) replacement one for $50. You will have to solder your connector onto the generic replacement. I do not think our host sells the generic replacements. It's the same O2 sensor as the $150 one, it just doesn't come with a connector attached.

Actually they do! http://www.pelicanparts.com/catalog/shopcart/911M/POR_911M_EXHmuf_pg5.htm#item18

Thanks for saving me a hundred bux!

84 911 WideBody · 84 911 WideBody's Garage

Quote:

Originally Posted by burgermeister

You can buy a generic Bosch (or other brand) replacement one for $50. You will have to solder your connector onto the generic replacement. I do not think our host sells the generic replacements. It's the same O2 sensor as the $150 one, it just doesn't come with a connector attached.

Dont solder the wire. refreance air for the sensor comes down the wire and you could poss. seal it off. Bocsh sells a weather pack conector to help adapt it to your application.

Roc Doc · 03-08-2009, 03:53 PM

Quote:

Originally Posted by 84 911 WideBody

Dont solder the wire. refreance air for the sensor comes down the wire and you could poss. seal it off. Bocsh sells a weather pack conector to help adapt it to your application.

Really? I've never heard of such a thing. Are you a wrench?

84 911 WideBody · 84 911 WideBody's Garage

Was at one time I am an Instructor for Navistar. But I was also a Instructor for Bosch for there BSC's

getluky · 03-08-2009, 04:21 PM

The install of that generic one is actually really easy. You just need a small pocket scale, side cutters, and a little time.

Porsche_monkey · 03-08-2009, 04:28 PM

Quote:

Originally Posted by 84 911 WideBody

Dont solder the wire. refreance air for the sensor comes down the wire and you could poss. seal it off. Bocsh sells a weather pack conector to help adapt it to your application.

Hotly contested. Do a search....

Roc Doc · 03-08-2009, 04:54 PM

Quote:

Originally Posted by getluky

The install of that generic one is actually really easy. You just need a small pocket scale, side cutters, and a little time.

What's a "pocket scale", and what do you need it for?

getluky · 03-08-2009, 04:58 PM

Oh, I was just talking about having a little ruler handy - the install instructions tell you to cut the OEM wire a certain number of inches away from the sensor, so it's handy to have a pocket ruler around to do the measurement. After you cut off the old sensor, it's a matter of refitting the heat sheathing, and all the wire connections happen with some twist-on and snap-in connectors, not through soldering.

This all assumes it's the same Bosch unit that I installed - judging from the pic of the generic Universal connector, it does look like the same. Good luck!

Roc Doc · 03-08-2009, 05:08 PM

Quote:

Originally Posted by getluky

Oh, I was just talking about having a little ruler handy - the install instructions tell you to cut the OEM wire a certain number of inches away from the sensor, so it's handy to have a pocket ruler around to do the measurement. After you cut off the old sensor, it's a matter of refitting the heat sheathing, and all the wire connections happen with some twist-on and snap-in connectors, not through soldering.

This all assumes it's the same Bosch unit that I installed - judging from the pic of the generic Universal connector, it does look like the same. Good luck!

I'm thinking what do I need weigh?

Thanks for the info.

burgermeister · burgermeister's Garage

Very nice to hear Pelican stocks the generic replacements.

The "air through the wire" argument seems beyond silly to me. FWIW, I soldered, heat shrunk tubed, and self-fusing silicone rubber taped mine, and it's been working just fine.

84 911 WideBody · 84 911 WideBody's Garage

Quote:

Originally Posted by Porsche_monkey

Hotly contested. Do a search....

and

Quote:

Originally Posted by burgermeister

Very nice to hear Pelican stocks the generic replacements.

The "air through the wire" argument seems beyond silly to me. FWIW, I soldered, heat shrunk tubed, and self-fusing silicone rubber taped mine, and it's been working just fine.

Do what you want to do. I will tell as per the Engineer from the factory that built them told me; Cut the end off your old sensor and use the weather pack to splice it back on the Generic O2 plug it back into the factory harness. I will say I have seen lazy/ slow responding sensor first had from Tech who put Dielectric grease in the connectors. So call it what you will.