Intermittant Short That Shuts Down Engine
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From: La Jolla California
Intermittant Short That Shuts Down Engine
I seem to have a strange intermittant short in my vette. I'll be driving along and all of a sudden the radio will cut off along with the light for my oil pressure gauge and tach light. Then the engine temp starts to rise which indicates that either/both the electric water pump and electric fans have shut off. During the next 15 seconds the engine starts to misfire and then just dies. Then after waiting for a couple seconds, I can restart the car and drive off with everything back to normal.
Any idea what would cause all of these unrelated electrical devices to stop working at nearly the same time? The fuses look OK and I can't find any obvious place in the wiring where there is a short. When the car dies, I normally pop the hood and start looking for a smoking short but never find anything.
Any ideas of how I should approach this problem?
Any idea what would cause all of these unrelated electrical devices to stop working at nearly the same time? The fuses look OK and I can't find any obvious place in the wiring where there is a short. When the car dies, I normally pop the hood and start looking for a smoking short but never find anything.
Any ideas of how I should approach this problem?
Racer
Joined: May 2000
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From: Port Orchard Washington
Re: Intermittant Short That Shuts Down Engine (Langadorf)
it sounds more like an intermittant open more than a short - vettes are notorious for having ground problems - clean all ground connections- also there is a plug on the passenger side of the engine compartment next to the heater box that has a couple of heavy gage red wires (along with some others) check for corrosion there - i had a problem there - dave
Le Mans Master
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From: Orlando Floriduh
Re: Intermittant Short That Shuts Down Engine (Langadorf)
Seperate and check the fuse block connectors in the engine bay at the firewall . These feed everthing and do get corroded over the years. I have seen them arced completely through but you cannot see it until you take them apart.
Melting Slicks
Joined: Dec 2000
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From: Carmichael CA
Re: Intermittant Short That Shuts Down Engine (silvervetteman)
I'm with silvervetteman :iagree:
Daves80 took me for a ride one day in his vette, and along the way the car just quit running. He reached into the engine compartment and worked the firewall fuse block electrical connectors which allows the inside electrical wires to be connected to the engine compartment wiring harness.
Daves80 took me for a ride one day in his vette, and along the way the car just quit running. He reached into the engine compartment and worked the firewall fuse block electrical connectors which allows the inside electrical wires to be connected to the engine compartment wiring harness.
Abby Normal
Joined: Dec 2001
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From: Press "2" for English
Re: Intermittant Short That Shuts Down Engine (Langadorf)
i'm thinking open also. check battery first. side post batteries suck. you might be able to find a problem just by seeing if the cables are loose enough to move on the posts. door light will go off and on if there is any open there. even if the bolts are tight, pull them off and clean out the corrosion you can't see under there. if that isn't the problem, check the hot terminal on the starter and the frame connection to the ground. it's possible you ran over something that didn't seem to do any damage but just may have gotten up on the cable-to-frame groung. so many unrelated circuits indicate a power problem at the source.
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From: La Jolla California
Re: Intermittant Short That Shuts Down Engine (clutchdust)
Well I checked the battery connections, block-to-frame cable, starter cable, etc. and everything looked OK.
It was dark when I checked the fuses the first time, so I gave it another look this afternoon. I don't know how I didn't notice this even in the dark, but look at this fuse and the fusebox in the pictures below.
I've never seen a fuse blow like this before. It looks like it blew but then melted and fused to a little metal piece that kept the connection working most of the time. Any ideas what would cause this?
I followed the pink wire that it fuses and it powers my Holley fuel pump and cooling fans as well as acting as the ignition signal to turn on my radio, shift light, and oil pressure light.
I'm assuming this is overloading the 30 AMP fuse. Would it be OK to just replace it with a higher amperage fuse or does this need to be rewired somehow? It has worked just fine with all these components hooked up for over a year and just started acting up recently.
Thanks for your help.
[Modified by Langadorf, 6:39 PM 4/7/2003]
It was dark when I checked the fuses the first time, so I gave it another look this afternoon. I don't know how I didn't notice this even in the dark, but look at this fuse and the fusebox in the pictures below.
I've never seen a fuse blow like this before. It looks like it blew but then melted and fused to a little metal piece that kept the connection working most of the time. Any ideas what would cause this?
I followed the pink wire that it fuses and it powers my Holley fuel pump and cooling fans as well as acting as the ignition signal to turn on my radio, shift light, and oil pressure light.
I'm assuming this is overloading the 30 AMP fuse. Would it be OK to just replace it with a higher amperage fuse or does this need to be rewired somehow? It has worked just fine with all these components hooked up for over a year and just started acting up recently.
Thanks for your help.
[Modified by Langadorf, 6:39 PM 4/7/2003]
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Joined: Mar 2003
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From: Toronto Ontario
Re: Intermittant Short That Shuts Down Engine (Langadorf)
All I can say is D A M N ! That little baby is fried, crisped and nuked some more. Well, I'd certainly say you found your problem. :hurray: Now just to prevent it in the future.
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From: Morinville Alberta
Re: Intermittant Short That Shuts Down Engine (StarLord)
The bad thing is that fuses don't just blow for no reason especialy like that You Have got to find out why it blew in the first palce. nextime it might be a fire.
and what ever you do don't put in a bigger fuse untill you check the diagram.
What does that fuse supply power to?
and what ever you do don't put in a bigger fuse untill you check the diagram.
What does that fuse supply power to?
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From: La Jolla California
Re: Intermittant Short That Shuts Down Engine (Aaron76)
and what ever you do don't put in a bigger fuse untill you check the diagram.What does that fuse supply power to?
It originally was for the auxillary electric cooling fan. Now, it powers the electric fan, fuel pump, and turns on the radio/shift light/gauge light.
The bad thing is that fuses don't just blow for no reason especialy like that You Have got to find out why it blew in the first palce. nextime it might be a fire.
[Modified by Langadorf, 8:33 PM 4/7/2003]
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From: Toronto Ontario
Re: Intermittant Short That Shuts Down Engine (Langadorf)
If I'm not mistaken, the point of fuses is so that when the load on the circuitry becomes too great, they blow before the circuitry does. I would not recommend putting in a higher rated fuse until you make sure that the circuitry and wiring can take it. If your system can only handle 30 amps at the most for example and you put in a 40 amp fuse, next time it'll be a fire in your wires. If as you said you added components to that fuse that it wasn't designed for originally, that nuked fuse may be a good indicator that too much current is being drawn on that system. Of course it could also be a totally different issue. All I'm saying is, be very careful and maybe get a better opinion from someone else who knows what they're talking about.
[Modified by StarLord, 11:16 PM 4/7/2003]
[Modified by StarLord, 11:16 PM 4/7/2003]
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From: La Jolla California
Re: Intermittant Short That Shuts Down Engine (StarLord)
The thing is, this circuit isn't performing the same function as it did from the factory. The electric fans on there now are aftermarket and replaced the mechanical ones. Also, the fuel pump is aftermarket and electric. I've read through the manuals on both items and neither mentions how much current they draw or recommend a particular fuse rating for them. The 10 gauge wire powering these items also may be non-stock.
Here is the external fuse holder I wired to fix it:
Tonight, I ran the car for about 10 minutes and then checked all the related connections near the fuse box. Nothing seemed hot and the fuse hadn't blown.
[Modified by Langadorf, 12:24 AM 4/8/2003]
Here is the external fuse holder I wired to fix it:
Tonight, I ran the car for about 10 minutes and then checked all the related connections near the fuse box. Nothing seemed hot and the fuse hadn't blown.
[Modified by Langadorf, 12:24 AM 4/8/2003]
Safety Car
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From: South Central Louisiana
St. Jude Contributor
Re: Intermittant Short That Shuts Down Engine (Langadorf)
IMO, I would connect the relay for the cooling fan direct to the alt wire in the engine compartment or the main at the starter.
Abby Normal
Joined: Dec 2001
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From: Press "2" for English
Re: Intermittant Short That Shuts Down Engine (71,454,4spd)
i've seen this happen a couple times on my car as well but it's always been a stand-alone fuse, generally the one for my e-fans. i believe it's happening because the power draw is just barely too much. either due to too high an amperage or too great a resistance in the circuit. both will generate too much heat. the deal is, your not drawing 33, 34 or 35 amps, it's probably more like 31 or 32. not really enough to blow it but definately warm enough to make it overheat. you could also be drawing right on the edge of available power (like i am) but over too great a distance. this will cause the heat build up issue, especially at connections like crimp connectors.
just my opinion, but anything you have added besides factory equipment, i would fuse separately. this will prevent you from over-amping on a modified factory circuit. also it will aid you in trouble shooting if you continue to have the same problem, you can then determine which item is creating the overcurrent situation.
just my opinion, but anything you have added besides factory equipment, i would fuse separately. this will prevent you from over-amping on a modified factory circuit. also it will aid you in trouble shooting if you continue to have the same problem, you can then determine which item is creating the overcurrent situation.
Drifting
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From: San Diego, CA Website: ChrisMitchell.us
Re: Intermittant Short That Shuts Down Engine (71,454,4spd)
IMO, I would connect the relay for the cooling fan direct to the alt wire in the engine compartment or the main at the starter.
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From: La Jolla California
Re: Intermittant Short That Shuts Down Engine (clutchdust)
Wiring them seperately sounds like a good idea to me also. Next time I'm working on it, I'll rewire the fans.
Thanks all for the input .
Thanks all for the input .
Pro
Joined: May 2001
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From: Yardley PA
Re: Intermittant Short That Shuts Down Engine (Langadorf)
Wirng them seperately is what I've done too. This should improve things for sure. However, looking at your melt-down, this is not an issue of the fuse, but too high a contact resistance that caused this excessive heat. If you clean the contacts there and make sure they work nicely you should not get any more melting/fire in that area. Again: a picture like this is NOT caused by the fuse.
Be careful, you don't want your baby to catch fire!
:cheers:
Stefan
Be careful, you don't want your baby to catch fire!
:cheers:
Stefan
