Yet another fuel delivery question (95 Jimmy) - amp draw of pump?

I am still hunting for my hard start solution and I noticed that the fuel pump relay in the glove boax runs very hot. I assume one of two things... A partial short in the wiring harness or a pump that's running too hard due
to a failing motor or similar... Here's my question...
Can I test amp draw for the pump from the relay socket or computer connection or similar?? Do I have to test the draw right at the pump connector? It is VERY tricky to access without dropping the tank. It doesn't seem impossible but it is the next closest thing to impossible..
Thanks. Andrew.
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You can test fuel pump amperage anywhere that is convenient. Current does not change anywhere in the circuit. You do need to compensate for any other powered devices that share the circuit though.
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wrote:

The relay gets hot when? You can check the current anywhere between the relay and the pump, not at the computer connection. If the pump was drawing too much current the fuse, if it's the correct one, should blow.
Al
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wrote:

If it helps any... When the pump in my suburban went it was drawing 18amps. After the pump was replace the new pump was drawing 2amps peak. I have heard of times were the wiring to the top of the tank corroded and in cases actually melted.
good luck, mark
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I just tested the amp draw on my pump from the test connector under the hood and I saw a fairly steady 8.6A (I checked for glitch capturing within 1A and nothing turned up). I scoped it while I was as it and it had a very steady wave with no real drops or rounded edges so either it's in fine shape or it's worn to a point that it doesn't fluctuate. I read somewhere that these high output fuel systems will have a draw up to 10A on a good pump. Can anyone verify this? I still think it's a nasty electrical issue with supply to the relay but I just wanted to update anyone who's helped out this far.
Thanks, Andrew.
in article 45d9db88$0$9861$ snipped-for-privacy@news.usenetmonster.com, r_d at rock snipped-for-privacy@hotmail.nospam.com wrote on 2/19/07 12:19 PM:

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Have you ever replaced the fuel pump relay? If the points get bad, the heat and resistance will increase. A badly worn relay can actually cause the pump to burn-out due to low voltage to pump motor.
James
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James,
I have replaced the EFI relay 3x to be sure that's not my problem. I don't think the issue is with the relay unless it's a bad/cold solder joint in the actual socket itself. Thanks. Andrew.
in article snipped-for-privacy@t69g2000cwt.googlegroups.com, James1549 at snipped-for-privacy@current.net wrote on 2/19/07 7:09 PM:

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If anyone knows the flow rate...I could calculate an estimated value based on the pressure, flow, efficiency and voltage.
Also, you might measure the resistance through the load side of the fuse to ground and compare that to a new pump.
wrote on 2/19/07 12:19 PM:

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I have a Tech2Tech article that suggests 28mmils at 60psi. I have a flowrate formula:
HPxBFSC ------- # of cylxMax Duty Cycle
240x0.4 96 -------- = ------- = 20lb/hr?? 6x.80 4.8
but I didn't look at it very hard. Do you know exactly whre the fuel pump is grounded at? I still suspect a ground differential. Thanks. Andrew.
in article 5vrCh.59379$ snipped-for-privacy@newssvr22.news.prodigy.net, News Skimmer at snipped-for-privacy@sbcglobal.net wrote on 2/19/07 7:36 PM:

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WTF is all that? Not sure what your formula is for. What unit is your flow rate in? not sure what mmils are...please spell out. also does that rate include the recycle...recycle must be included in the horsepower calc.
On the c/k's, the ground peels out of the harness / plug near the pump and bolts to the frame. If it is a ground problem, I don't think that would lead to excess amps.
skimmer
wrote on 2/19/07 7:36 PM:

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Sorry - I was just pluging in some numbers based on a formula I have seen used. The formula is for flow rate based on Lbs/hr. I believe that it's used to determine injector sizing with modified motors. BSFC (Brake Specific Fuel Consumption as a calculation of lbs per horsepower-hour) , Max Duty Cycle set at .80 b/c most injectors would burn up b/w 90-100 I would think). Mils (volumetric 1000th of an inch) 'mmils' was a typo.
Anyway, forget the formula - I was just playing with a formula I had seen used - as for recycle rate - I don't know.
Thanks for the feedback. As for the grounding issue - I'm not so concerned with high amps now that I know 8-9A is on the normal side for these fuel systems - the pump will run intermittently at startup meaning that sometimes turning the key won't engage the pump motor. I thought maybe a bad ground could be to blame...
Thanks again! Andrew.
in article DlOCh.47984$ snipped-for-privacy@newssvr21.news.prodigy.net, News Skimmer at snipped-for-privacy@sbcglobal.net wrote on 2/20/07 9:43 PM:

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Maybe this weekend I'll measure the amp draw on my 99 5.7r
My 93 4.3z TBI with a new bosch pump pulls less than 2.
Based on the 2 at 10-12 psi, 60 psi would raise the amps for the same flow to 10
skimmer
wrote on 2/20/07 9:43 PM:

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Once again - I appreciate the help. I was able to confirm that 8-10A is acceptable for a 60psi Vortec fuel system so you needn't worry about metering your trucks for me. I will post again if I solve the intermittent no start issue. As a gesture of good faith, I pulled almost every harness on the truck and packed them with dielectric grease. I sanded and refitted all the engine grounds also. I didn't put any grease in the computer molex connectors because I was a little leary about that even though it's likey to be fine. I have yet to remove and sand down the fuel pump ground but it's next on my list. Failing all of this, I will replace the entire relay 'convenience center' in the glovebox and then start metering outputs on the computer.
Thanks! Andrew.
in article PZQCh.31049$ snipped-for-privacy@newssvr27.news.prodigy.net, News Skimmer at snipped-for-privacy@sbcglobal.net wrote on 2/21/07 12:43 AM:

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Intermittent no starts (no fire/no fuel) can be caused be a bad ignition module.
On the fuel pump relay...you might consider removing it and powering the pump directly with a fused jumper through the load side of the fuse.
On my 93 c1500, you can power the pump through one of the OBD1 connector pins which then passes through the fuse. You might need to check your wiring diagrams because that pin might not work if the relay is pulled out or arc'd close (welded closed in run position). I think my test connection opens when the relay closes. Make sense? probably not but study your schematics.
skimmer
wrote on 2/21/07 12:43 AM:

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Skimmer,
Thanks again. Are you saying that I should run a jumper from the relay socket to the fuse panel? I assume you mean strictly for testing purposes? If I were to leave that connected, it ranks up there with dumnping fuel into the carb with the wiper pump... Your thoughts on the ignition module may be a good place to look. My only concern about that is if I power the pump via the test connector under the hood, she fire right away. I've never had such a battle with an electical gremlin to date - I'm almost ready to take it to a tech even though that's against my religion (with the exception of tranny/drivetrain work).
I'm still not sold on the fact that the ignition sewitch might be causing these issues... At $200 for a replacement I'm not ready to gamble on it yet though. The reason I suspect maybe the ign switch might be to blame is that I can turn the key to ACC several times before the pump engages. Once the pump engages, it starts right up. Some day I will figure this one out. I'm still secretly hoping that someone with the same issue will reply with a fix... Thanks! Andrew.
in article JLaDh.130$ snipped-for-privacy@newssvr17.news.prodigy.net, News Skimmer at snipped-for-privacy@sbcglobal.net wrote on 2/22/07 1:28 AM:

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Ok I finally got it! I tested the GRN/WHT continuity from the steering column to the relay harness and it was fine. I tested the continuity from the ECU to the relay and it also checked out. I then verified trigger at the relay and also was able to run the pump with a jumper on the load side of the socket. I verified 2 relays to be working flawlessly and had the same intermittent results with both of them. The problem?? The connector on the pump side of the socket was loose internally (hence it tested ok when pressed with my probes on both sides but was intermittent when standing alone. Some **very** carefull bending with a pick on that damn terminal seemed to lock it in place and solve my problem. It starts every time now. Vvrrooommmmmm... Case closed!
Thanks for all your help! To think I was about to throw an ignition switch and crank sensor at this problem... Andrew.
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I am glad to see you found your problem. I'm going to just bullet some thoughts so you'll know for next time.
*You should find and study a wiring diagram and locate each connection on the vehicle...then you will figure out the shortest/direct path to the load. On my c/k, a good place is through the fuse on the engine side of the firewall by the evaporator. I don't know where your fuse is located or where it compares to the socket on the relay...but either report to the pump. If you bypass the fuse...provide a fuse in your jumper....or else $%&#$
*Testing (the pump) through the relay can go crazy if the contacts have arc'd or something weird has happened.
*Testing through the OBD connector is okay if it has one.....although that circuit opens when the relay closes.....at least on mine.
*Not sure what you mean on the fire and dumping fuel, etc. When the fuel pump is hot-wired, fuel will only recycle to the tank unless something is pulsing the injectors.....like cranking or the engine running...i.e. reference pulses being received from the distributor. If you are dumping fuel, your injectors are leaking.
I hope you read this and it helps.
skimmer
wrote on 2/22/07 1:28 AM:

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Thanks for the helping hands.
Take care, Andrew.
in article KLIDh.722$ snipped-for-privacy@newssvr25.news.prodigy.net, News Skimmer at snipped-for-privacy@sbcglobal.net wrote on 2/23/07 4:11 PM:

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