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#1 |
Enough already!
Join Date: Oct 2009
Location: CT
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![]() 1986 745T, 157,000 miles.
I found that the #1 fuse (fuel pump, Engine Management, ETC) is getting very hot. Almost to the point of not being able to touch it. I've read that the main fuel pump should draw 6.5 amps. Where would I check that? I connected my amp meter across the #1 fuse and found it was drawing between 10.5 and 12.1 amps. Seeing that high amperage, I elected to replace the main pump. So I put the new pump in and am still drawing 11.5 amps across the #1 fuse at idle. Maybe that's a combination of the pre-pump + the main pump? When I replaced the fuse panel a few years ago (due to meltage), I was very careful to clean and solder all the crimp connections. All were very clean to begin with. At that time, I replaced the fuel pump relay and drilled cooling holes in the relay body too. Additionally, I removed the #1 wires from the fuse panel and replaced them with a separate "stand alone" 30 amp fuse holder (though I only use a 20 amp fuse). Just to be clear, after isolating the #1 wires from the fuse panel, the fuse panel and fuel pump relay do not get hot anymore. Is it likely that the original pump was fine? Is 11.5 amps across #1 normal? Should I really be able to burn my fingers by touching the #1 fuse? That can't be right. Could the Engine Management or ETC be causing this? The engine does have a slight intermittent hiccup at idle. |
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#2 |
Board Member
Join Date: Sep 2009
Location: near baltimore
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![]() Never mind, just realized I already tried to help on Brickboard yesterday.
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-Art Last edited by cleanflametrap; 09-28-2012 at 10:32 AM.. Reason: redundancy |
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#3 |
Enough already!
Join Date: Oct 2009
Location: CT
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![]() Don't take offense.
I just thought I'd post it here too. Thanks. |
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#4 | |
Broad Member
Join Date: Jan 2011
Location: norte carolina
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![]() Quote:
*NOW* I understand why a lot of the pleas for help never "get closure".. once the problem is solved *elsewhere* we never hear of the resolution... ![]()
__________________
In a closed society where everybody’s guilty, the only crime is getting caught. In a world of thieves, the only final sin is stupidity. |
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#5 | ||
Board Member
Join Date: Sep 2009
Location: near baltimore
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![]() Quote:
![]() http://www.brickboard.com/RWD/volvo/..._amperage.html Quote:
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#6 | |
Broad Member
Join Date: Jan 2011
Location: norte carolina
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![]() Quote:
PESSIMIST: "The glass is half empty!" ENGINEER: "The glass is the wrong damned size!" ![]() |
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#7 |
Board Member
Join Date: Sep 2009
Location: near baltimore
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![]() --http://bangengineering.com/blog/wp-content/uploads/2007/05/dilbert_optimist-pessimist-engineer.gif--
Last edited by cleanflametrap; 09-28-2012 at 05:09 PM.. |
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#8 |
Broad Member
Join Date: Jan 2011
Location: norte carolina
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#9 |
Enough already!
Join Date: Oct 2009
Location: CT
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![]() It's been a few years, but this problem reappeared last fall. Left me stranded and I got it towed home and it hasn't moved since. Spring is here and my 17-year old wants to learn to drive a stick so it's time to fix it.
Cliff notes version of what happened last November... After about 10 minutes of driving, the fuel pump wire went up in smoke. Strange that the fuse holder melted but the fuse didn't blow. Fortunately I separated the fuel pump wire from the fuse box years ago as stated above. In these intervening years, I've learned about the biodegradable wiring harness. I did see some missing insulation on the ground wires near the intake manifold but haven't investigated further yet. Would it be likely that the deteriorating wire harness is the root of the problem? Again, the fuel pump wire and its independent fuse is isolated from the fuse box. |
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#10 | |
Board Member
Join Date: Sep 2009
Location: near baltimore
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![]() Quote:
Given the wire is already separated from the fusebox, you should be able to replace just that wire, and splice in a new fuseholder. Last edited by cleanflametrap; 03-27-2017 at 07:59 AM.. |
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#11 |
Enough already!
Join Date: Oct 2009
Location: CT
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![]() "excessive heat (enough to melt things) in an electrical circuit is local in origin"
That is key. You know, I never even thought that the fuse holder I installed could have been at fault. Though it was a 30A holder, who knows what quality its connections really are/were. First step, replace that fuse holder...again. Thanks |
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#12 | |
Board Member
Join Date: Sep 2009
Location: near baltimore
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![]() Quote:
Of course the circuits drawing the highest current continuously (with the motor running) are going to be the most vulnerable to contact resistance increase. And the fuse associated with those continuously run circuits is going to be hotter even when the connections are still good, because a fuse element needs to operate at elevated temps if it is going to melt (perform its function) when the current is actually exceeded. |
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#13 |
Board Member
Join Date: Jul 2009
Location: Atlanta
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#14 |
Enough already!
Join Date: Oct 2009
Location: CT
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![]() All right then, here's this weekend's project...
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#15 |
<Master Tech>
Join Date: Nov 2002
Location: California
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![]() http://www.forums.turbobricks.com/pi...pictureid=2916
I am practicing current measurementsituation of the fuel pump using a scope and an amp clamp. Hard to see in the pic, but according to my test I was only pulling about 2 amps, but I may have the settings wrong. I think it was gseelster that told us he measured closer to 6 amps on his tests. Google search says average draw is about 1 amp for each 10 psi fuel pressure: http://www.underhoodservice.com/fuel...-current-draw/ 12 amps seems too high.
__________________
No Start Thread |
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#16 |
Board Member
Join Date: Sep 2009
Location: near baltimore
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#17 | |
Board Member
Join Date: Sep 2009
Location: near baltimore
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![]() Quote:
Looks something like this tank pump drawing about 2A. (8 years ago on turbo brick 242Ti) ![]() |
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#18 |
Enough already!
Join Date: Oct 2009
Location: CT
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#19 |
Board Member
Join Date: Sep 2009
Location: near baltimore
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#20 | |
Enough already!
Join Date: Oct 2009
Location: CT
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![]() Quote:
It will be easy to check again with the fuel pump isolated from the other items powered by fuse #1. I'll check both the fuel pump and then across fuse #1. |
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#21 |
Board Member
Join Date: Oct 2014
Location: Tallahassee, FL
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![]() ![]() Also, an infrared thermometer can detect high resistance just by finding the heat. Find the heat, find the problem. If you've got money falling out of your ass, look into those FLIR scopes.
__________________
1978 245DL - B21 Penta carb powered! 1982 244T - Crushed 1983 245DL - SOLD 1984 244DL - Crushed 1984 245DL - Sitting in someone's yard 1991 740SE - girlfriend's car ![]() 2008 S60 2.5T - Money drainer |
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#22 |
Enough already!
Join Date: Oct 2009
Location: CT
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![]() Nope, 54 year old sphincter is still tight so I won't be laying out extra cash.
Those are neat little meters in your post, but I'll just use a plain old digital multi-meter. |
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#23 |
Enough already!
Join Date: Oct 2009
Location: CT
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![]() Got to it today.
I elected to not install the fuse holder that I purchased and is shown above. Instead, I just installed a new fuse in the female ends of the wires that would normally go to fuse #1 in the fuse panel. Took it for a 20 minute ride and did not find the fuse getting hot. Maybe it's fixed, who knows. Time will tell. |
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#24 |
Board Member
Join Date: Apr 2009
Location: Cincinnati, ohio
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![]() In the same boat here. #1 fuse getting hot. I took a donor fusebox from a 740 so, I have parts. I am intrigued by "Instead, I just installed a new fuse in the female ends of the wires that would normally go to fuse #1 in the fuse panel." idea. I thought about that being an option but, there is a heavy guage brown wire also plugged into the #1 fusr holder from underneath. Does that heavy brown wire have to be dealt with at all? Also, how did you access the wires? I have the knee bloster off but, the kick panel isn't budging. Thanks.
__________________
1993 940 8 valve turbo 70000 miles 1991, NA 244DL 111000. |
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#25 |
<Master Tech>
Join Date: Nov 2002
Location: California
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![]() Voltage drop test can reveal bad connections, such as at a fuse.
Also, use a test light instead of a dvom. One strand of wire, or a weak connection, will pass 12v and can lead to false conclusions. I got popped by it last week: had 12v going to a motor and misdiagnosed it as a bad motor, but it really had 12v and poor current thru the wire. A noid light and a test light would NOT illuminate on the same plug a measured 12v on with a dvom. We also do a drag test to reveal poor connections. Maybe bust a blade off a spare fuse and drag it in and out of the terminal and compare it to a known good one. Crimps also go bad over the years from heat. I see more and more bad connections on modern cars with all their light 20-22 guage wiring and tiny little terminals. Old Volvos have nice thick 14 guage wires and huge spade terminal connections compared to the modern stuff. I would probably start with a new terminal on each side of the fuse. I dont know where you can get them, but de-pinning and crimping on a new terminal is a great proper fix and a good starting point. I would also make sure anything on the circuit has a good clean ground. Last edited by ZVOLV; 09-20-2017 at 03:15 PM.. |
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