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Old 10-30-2018, 10:01 AM   #1
MIKESAD50
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Close to disaster

Drove the truck home last night and filled with fuel on the way home. got home and was hearing a screeching type noise and figured it was related to the neighbors.
annoyed at the noise after 1/2 hr+ went out to find out what was causing it. found fuel pump in the truck running and pump unit in tank was warm.
Went to the cab to check relay and found relay box hot and relay really HOT to hot to touch. got relay out of relay/fuse panel under seat.
not sure cause yet. hope it is just a bad relay that stuck closed and ran pump for all that time. Might have a ECM issue that kept the relay engaged, possible wire issue also. need to start with getting a new relay and see where I'm at.

Never heard of the relay brand and it is one of the relays that came with the fuse/relay panel from GMPP with the connect and cruise kit.

the relay was very HOT for 15-20 minutes after removing, I think not far from a fire.
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Old 10-30-2018, 10:06 AM   #2
1957 Chief
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Re: Close to disaster

Not good my friend. Glad you noticed it. And I have used a ton of those mini relays and kinda makes a fella wonder now...

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Old 10-30-2018, 10:13 AM   #3
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Re: Close to disaster

I would not be surprised at a warm relay, but hot is not normal under normal circumstances. This leads me to believe the issue is 1 of 2 things - faulty relay, or excessive amperage draw. My fear would be that the relay was not the issue, excessive power consumption caused the relay to fail.

I am not familiar with that pinout. The pin that has seen a lot of heat, what is that pin used for? Input from the battery?

What size fuse do you have on the input wire? What amperage is the relay rated for?

EDIT:
Even if the ECM did hold the relay open, I would not expect this kind of damage.
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Old 10-30-2018, 10:19 AM   #4
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Re: Close to disaster

The truck had not been running just the pump running for all that time. That was the pin for the feed to the fuel pump. I suspect stuck relay or signal/signal wire from ECM telling relay to stay closed after shutting the truck off. I dont recall hearing the pump running when I shut the truck off but was long after going into the house I strted to hear the strain of the pump. sounded like a pump running dead headed, but this was running to the regulator and by passing back to the tank but struggling after all that time.
I do know warm relays are pretty normal. This was HOT HOT.
relay is a rated at 35a from what I'm finding only while looking for a replacement.
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Old 10-30-2018, 10:32 AM   #5
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Re: Close to disaster

That is scary stuff!

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Old 10-30-2018, 02:58 PM   #6
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Re: Close to disaster

wow, that couldda ended badly. good thing you didn't go tear the neighbor a new one, lol.

that relay is pretty standard and used for everything from remote start kits to fog lights. there must be a current draw issue or you just got a bad or mislabelled relay.

ok, before I continue, don't get me wrong here, I'm not saying your truck was wired wrong or craftsmanship wasn't top notch. anybody could look at your build thread and say that would be a huge stretch, it looks factory for a newer car and the component layout is awesome. I'm just giving some ideas with the assumption that some first timers will also be reading your posts and someone may benefit.

I would start with: (don't turn the key on yet)
-check the wire size and length of run from the battery, through the relay and pump and out to ground, against the chart to ensure the wiring is large enough to safely support the current draw of the pump spec with some left over as a safety margin. ensure the ground in included in the dimension
-check wiring all the way back to the pump unit and to ground. looking for any heat issues where the insulation on the wire looks like it got hot. ensure the wiring is away from other heat sources as well, like exhaust etc. if there are any wiring connections in the run make sure to check them closely to ensure they are good for the current draw and are properly insulated and sealed (double wall shrink tube)
- do a draw test on the pump, separate from anything else. directly wired to the pump (through a fuse) where the relay was and also the amp meter with no ecm, relay etc. this will check the amp draw on the entire circuit from the relay back.
-do an amp draw on the pump where the wiring comes out of the tank and connects to the wiring going to the relay. I assume there is some sort of connection there and a length of wire running forward. this will eliminate any wiring issues, forward of the pump, and will let you know the actual current draw the pump is using. run the pump for a few minutes to allow it to heat up if it is going to. since you said the pump was making noise I would suspect the pump now, even though it may not have been your initial issue, because there are plastic impellers running inside plastic housings. once they run that long without fuel actually moving through them to help cool the parts they become suspect in my mind.
-compare the draw test against the pump spec and see how it compares
-pull the pump from the tank and check for poor connections inside the tank. I have personally seen wiring inside the tank with the insulation melted right off the wire.
-check the ecm circuit wiring diagram to ensure you know how that circuit is supposed to be wired, ecm supplies power to operate the relay or ecm supplies a ground to operate the relay, then check to ensure the signal wire from the ecm is doing what it should be with the key off. if it is not operating correctly check the wiring all the way back to the ecm. a cause may be a melted wire in the loom somewhere which is short circuiting a power or ground supply from another circuit into your signal wire which is turning on the relay. if there are no issues found with the wiring circuit it could be a possible ecm issue and would require testing on the ecm by itself.
-repair any wiring issues or pump issues. make sure there is a fuse, of the correct amperage for the draw from the fuel pump or as recommended from the pump manufacturer, placed inline on the power supply circuit before the relay. usually placed at the beginning of the power supply for that circuit. this can be, and often is, a "hot at all times" source in the fuse panel but this method can make the pump continue to operate if the relay sticks or otherwise malfunctions. if wired to a "hot with ign on" source your fuel pump would shut off immediately when the ign is turned off, whether the relay malfunctioned or not. this method does, however, place more strain on the actual ignition switch connections
-I always recommend the use of an oil pressure safety switch in the circuit if the ecm doesn't control that function or if using a carb style fuel system. this would shut down the fuel pump if engine oil pressure is lost. a good quality relay and proper relay plug terminal for the relay is a great idea as well. good quality crimp connection terminals, done with good quality crimp tools and protected with double wall shrink tubing is also a great idea. some crimp connections have solder inside as well as having built in shrink tube around the connection. this is awesome because it takes less time to do each connection plus the shrink tube always fits the connector properly.
if everything else checks out then one would assume the connection at the relay was possibly faulty and caused heat to build and may have caused the terminals inside the relay to weld together. this caused the pump to continue running even though the signal to the relay was off.

attached is a current draw/wire size chart from the net that I use and have had no issues with. maybe useful for somebody

here is a link to the holly page on fuel pumps. scroll down for a couple of ways to wire a fuel pump using the oil pressure switch. maybe useful for somebody as well

https://www.jegs.com/InstallationIns...0-12-801-1.pdf
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Old 10-30-2018, 03:09 PM   #7
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Re: Close to disaster

here is another link to fuel pump wiring basics.
again, same disclaimer as the last post. great looking build you have there.

http://www.enginebasics.com/Advanced...p%20relay.html
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Old 10-31-2018, 01:46 AM   #8
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Re: Close to disaster

My similar experience ended up being simply a bad relay. I changed the relay and it's worked fine ever since.
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Old 10-31-2018, 03:06 AM   #9
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Re: Close to disaster

I would not assume that it was just a bad relay. I would follow what Dsraven suggested to the letter. I'd also make sure that the fuse was the correct amperage. I like relays but the trouble with them is that we don't always run the power feed to the relay through a fuse and the circuit ends up not being fused and the only thing that is fused is the wire from the switch that triggers the relay.
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Old 10-31-2018, 07:25 AM   #10
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Re: Close to disaster

Quote:
got home and was hearing a screeching type noise and figured it was related to the neighbors.
Sorry, but that made me chuckle. At least you didn't mention your wife...

Here's some practical advice, one tech to another. I have not proven, but firmly believe, those relay amperage ratings are for peak, brief, intermittent current draw. There's no way a constant 30A draw won't burn one up. Most of the time the female terminal(s) it plugs into will heat up, then the terminal relaxes and current starts to arc across the gaps which are created. Then the heat begins to build, the terminal coatings oxidize, and finally the relay and the box it plugs into melts.

Manufacturers are doing everything they can to save money these days and in the fleet world we see the results. GM uses similar relays in the underhood connectors of their vans. 16-17A continuous draw through the fuel pump as our vehicles drive through town destroys the board where the relay plugs in. While GM was willing to replace the boards under warranty we let them. Once the vehicles are out of warranty we move the relay off-board and use a fuel pump relay from a '90s design truck. We also make sure to use female spade terminals with a spring terminal rather than the cheapie side-contact aftermarket versions. I even worked to locate a relay block with quality spade terminals.

The same thing happens with horn relays, blower relays, ABS motor relays, and body builder added A/C and fan relays. Those small pin relays just don't hold up like a relay with a larger pin. A number of our Chrysler vehicles have a similar problem to the GM vans I described. When I heard about the problem I ordered the Chrysler factory fix-it kit. It comes with a similar type of relay to what we use with the GM vehicles, and a plug with large spade terminals to connect the relay. Whaddaya know... The engineers seem to know the little relays aren't going to hold up in that circuit.

And in addition to the constant draw problem I mentioned you have to watch for current spikes. These happen primarily in circuits that power motors. Brush type motors act as a dead short when first powered on. As the armature begins to turn the current draw decreases. Each time a relay closes to power a motor there is a small arc across the contact points. The arc attempts to weld the contacts closed. If the points get hot enough they will try to stick. The size of the points and the size of the spring that forces the points to open back up are a big part of what prevents the relay from sticking. The type of metal the points are made of makes a big difference also. Quality relays use an alloy less prone to arcing and less likely to weld together. Bigger relays usually have larger points and larger return springs.

I used to have a chart from a GM trainer that listed GM fuel pump current draw vs fuel system type. System pressure was the real key. TBI was lowest at 9-13 psi. For systems with 55-65 psi, a typical GM pump draws 16-17A. Higher pressure draws even more current. My advice is to move to a larger relay after checking the pump and pump circuits for peak and constant current draw as mentioned above.




Last edited by 1project2many; 10-31-2018 at 11:50 AM.
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Old 10-31-2018, 08:31 AM   #11
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Re: Close to disaster

Where can we find that pictured relay?
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Old 10-31-2018, 08:54 AM   #12
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Re: Close to disaster

one project just nailed it. the smaller the pin on the relay the more apt they are to overheat with a decent draw over long term. personally, I like the ones with the larger spade terminals for this reason. I have also used the large, old fashioned battery isolator style that looks like the ford starter relay from the 70-80's vehicles.

https://www.amazon.com/Bosch-3322091.../dp/B0010AH6YM

here is a quick shop lesson on relays and different styles that may look the same but have different insides. some have diodes to help protect the contacts from induced current backflow from the load.(loads with a winding can have induced current when the magnetic field around the winding collapses as power is taken away). anyway, just know there are different types

http://www.autoshop101.com/forms/hweb2.pdf
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Old 10-31-2018, 11:46 AM   #13
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Re: Close to disaster

Quote:
Originally Posted by jjzepplin View Post
Where can we find that pictured relay?
That is a fuel pump relay used in many trucks including 89-99 C\K series.

If you are scrounging parts it can be found in the engine compartment on the passenger side under a black cover.
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Old 10-31-2018, 12:50 PM   #14
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Re: Close to disaster

here is another option to consider. notice the power and load terminals are twice the size of the switching signal and ground terminals. maybe they are onto something. rated for 30 amps, dunno if that is peak or constant. dunno if there is a pigtail available. just info

https://www.eeuroparts.com/Parts/530...ay-191906383C/
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Old 10-31-2018, 01:02 PM   #15
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Re: Close to disaster

here are a few part numbers for a 70 amp relay. you would or should upgrade the wiring and terminal connectors at this point to support a potential 70 amp draw.

Floesser 2270 relay; equivalent relays are:
Mercedes: 000 542 97 19
Audi/VW: 443 951 253J, 8D0 951 253, 4H0 951 253
General Motors: 90226846

looks like gm used this relay for windshield wiper motors
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Old 10-31-2018, 06:25 PM   #16
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Re: Close to disaster

We use those wide terminal relays in some of our systems to drive the triple condenser fans or the double evaporator fans. In some cases they run both. I would consider that to be a reliable option for up to 45-50A continuous. They are also used in Ford ABS motor circuits and in some of the diesel systems as well.

Looks like the Mercedes # is actually a round pin relay with a 40A fuse installed in the relay (see photo below). Very cool.

Here's a relay with wide terminals and a socket:
https://www.amazon.com/VF7-11F11-S01.../dp/B00EA5H6P8


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Old 10-31-2018, 08:00 PM   #17
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Re: Close to disaster

So I agree with every thing that has been pointed out. I figured sine it was the supply out to the pump, most likely due to excessive pump draw.
I got a new relay from Chevy dealer. It fits different years and models for everything from engine cooling fan, starter, fuel pumps, fog lights, etc.
I installed it and drove the truck for a few minutes, everything acted normal and seemed normal. I parked and let it sit and nothing abnormal, all worked as it had. I unplugged the relay and have left it out.
I planned on taking back to the shop and for sure checking for wire chaffing issues, and also amperage draw on the pump. I will pull my receipt folder for wire size. I believe it was 10 gauge to the pump both power and ground. It looks like the same 10 gauge in the relay box supplied by GM with the kit.
The pump sounded normal yesterday after new relay and a short drive. I checked on Aeromotive and they say it should be in the 15-19amp normal draw at 60psi to 90psi. They also recommend 10ga wire.
the fuse is the maxi fuse in 30a and was wired and supplied also in the relay/fuse box
Hope to find something for sure to blame but will be afraid to leave the relay in let alone power connected. I have thought of going to a Bosch style relay that I have been using and has been used for ever. just for piece of mind, and also may need to replace female terminal in box due to the heat, it looks good but slightly melted the box at that terminal and not sure I will be able to get it let alone get it or a new terminal properly seated and locked in the relay box
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Old 10-31-2018, 08:16 PM   #18
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Re: Close to disaster

As far as the different relay's mentioned the Volvos I have worked on for years have used many of those, plus some.
When I got the relay out of the box I was surprised at the size of the 30 and 87 pins, considering its a fuel pump its supplying power to. They are using the same relay as the engine cooling fan also.
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Old 10-31-2018, 09:36 PM   #19
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Re: Close to disaster

Quote:
They are using the same relay as the engine cooling fan also.
That's crazy. I wonder how many non-tech people get caught by this stuff.
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Old 11-01-2018, 07:36 AM   #20
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Re: Close to disaster

Quote:
Originally Posted by 1project2many View Post
That is a fuel pump relay used in many trucks including 89-99 C\K series.

If you are scrounging parts it can be found in the engine compartment on the passenger side under a black cover.
WELL Thank You! Cheap and reliable and weather resistant to boot!
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Old 11-01-2018, 07:43 AM   #21
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Re: Close to disaster

Why wouldn't a stock LS based vehicle relay work? Haven't they worked for decades? I know you could upgrade but why?
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Old 11-02-2018, 09:15 PM   #22
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Re: Close to disaster

Master disconnect.
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