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  #1  
Old 08-30-2010, 08:53 PM
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Default '87 Blazer fuel pump RELAY location?

Hi - I'm having the turns-over-but-no-start problem I've found a lot here have and now need to find where the RELAY for the fuel pump is, and the fuse for same. IGN and CRANK fuses are fine (if it's in that?)

1987 S-10 (downsized), 2.8L, 4WD, TBI, fuel filter behind power steering pump - that version!

I already took off the old fuel filter and that is clear. (I would have replaced it but NAPA's part has a 1mm too-big nut on it to fit in the bracket hex hole...)

Symptoms -

Truck started with slightly longer cranking to get me home from work, then would not start next morning. Has not started despite time (3 days) and half a dozen attempts (unlike some where time and later attempts work.)

No fuel pump whine when ignition first turned on (tip #1 after fussing with fuel filter.) Need to be sure pump is getting juice (fuse and relay good.) Plan to just replace relay once the right one is identified but can swap to test.

Have also tried tapping on the gas tank with ignition just turned On (to free fuel pump, tip #2.) None of this makes any difference, cranks great but makes no attempt to catch.

Thanks!
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  #2  
Old 08-30-2010, 09:12 PM
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On the firewall beside the brake booster. There is 2. One is your FP, the other is your horn... Switch them and see if your horn and fuel pump works... they both look like little black boxes about 1 inch cubed. There is also a wire sticking out of the harness no more than 2 feet from the relays along the firewall, the wire might be PINK (not 100% certain on color) and have a female connector on it that is not plugged in anywhere. That will be your fuel pump bypass. You can apply 12V to that wire with a wire leading to the battery (+) and power the pump sans relay for testing.
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Old 08-30-2010, 09:39 PM
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Wow! thanks for this, ohsofly! It's dark out now but will check in the light and post what I find.
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Old 08-31-2010, 05:41 PM
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Red face Relays not on firewall

Hi Ohsofly or anyone who knows this model -

My vintage does not appear to have any relays (as you describe, 1" black cubes) on Firewall. See pic of Firewall. Not much on firewall (wiper motor? flat black electrical thing about 3" square by 1/2" deep?) What's by the brake booster looks pretty complicated and they are not the same though right next to each other with major wire harnesses coming out of/around them, one is about 1"x2" the other about 1"x3". See Brake thingies pic.

It does appear to have 6 relays (only 5 are connected) on the top left side of the engine compartment. See Left engine comp relays pic. Including 2 that look identical, both connected, circled (One of Two Same closeup pic with legible writing.)

What the firewall does have is an unconnected female connector with tan/white stripe lead - could this be the fuel pump test lead bypassing its relay? (see unconnected female pic) This connector is circled, also on firewall pic behind transmission dipstick.

So if anyone can sort out what I have, have I found the horn and fuel pump relays and which ones are they? So if I switch them I can check that way if it's the relay that's bad.

To use test lead from fuel pump - if that's what the tan/white unconnected lead is - do I just connect it to the hot battery terminal? Does the ignition have to be On (before Start)? Any more wanrings about this (like connecting unidentified leads to positive)?

At this point I am thinking they only made a few hundred '86/'87 Blazers the "same" during the crossover...

Thanks for your assistance.
Attached Images
File Type: jpg Firewall-NoRelaysr.jpg (23.0 KB, 40 views)
File Type: jpg OneOfTwoSameRelaysr.jpg (27.6 KB, 36 views)
File Type: jpg UnconnectedFemaleLeadByFirewallr.jpg (29.6 KB, 42 views)
File Type: jpg LeftEngineCompRelays.jpg (30.4 KB, 62 views)
File Type: jpg BrakeThingier.jpg (33.9 KB, 27 views)
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  #5  
Old 08-31-2010, 05:57 PM
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Your 4th pic from the left shows the relays. There are 4 of them between your coolant bottle and I assume your windshield washer fluid bottle. One of those 4 is your fuel pump relay.
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Old 08-31-2010, 09:51 PM
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Yes the fuel pump relay is going to have that extra tail before it for bypassing it. And no, add 12v to it when the key is off to isolate the system. Then see if you can start it up bypassing when the key is on. Then you have found your problem. Also switch those 2 you have circled in that photo and try it out.
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Old 09-01-2010, 03:39 PM
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Guys - the 2 identical relays both seem to serve the horn: they are wired to each other and both have leads that go down to the horn. Doesn't a horn have 2 pitches? Maybe this truck has a relay/circuit for each pitch.

So I explored those other 3 relays (similar housing, different numbers) (there are 4 in the 4th pic but only 3 right ones are wired) next to the 2 identical relays and found only one that has a tan/white stripe lead coming out of it - matches the unconnected female on the firewall I found (hard to see color or connector in unconnected female pic.) NAPA confirms this p/n (10034222 LF 1273) can be the fuel pump relay p/n. This relay has a crack in the top housing and filthy connectors (oil and/or rust) - looks bad to me w/o even opening it up!

So unless this contradicts your experience, I'm ready to connect the female tan/white lead and bypass this relay per Ohsofly's directions, which I understand - and hopefully confirm it is just this rotten old relay and not the pump! What gauge wire do I need to connect battery to lead, same as tan/white lead (looks like about 18 gauge)?

Awaiting your confirmation between raindrops - thanks for this assistance!
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Old 09-01-2010, 04:59 PM
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Equal or larger wire. If you have the means, put a fused wire in so the fuse blows instead of something else if it isn't correct, but it sounds like it is the right wire.

You can swap the relay with one of the other ones to troubleshoot as well.
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Old 09-01-2010, 05:13 PM
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Gents - I couldn't wait. Built a little connector and hooked 'er up - fuel pump whines with key off. Did not try to start now (battery getting low) but no fuel pump (whine) was whole symptom and this bypasses the problem, so I am sure it's the relay, will pick up a replacement in the a.m. Sound right to you? Thanks!

My reply was out of time, Swartlkk, sorry. Nothing blew. All will be good soon. Thanks!!

Last edited by swartlkk; 09-01-2010 at 05:17 PM. Reason: *Consecutive Posts* - Please use the edit feature to add more information to your post if another member has yet to reply.
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  #10  
Old 09-01-2010, 05:17 PM
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Just food for thought then. Once you make up a fused jumper wire, it comes in handy for any kind of electrical testing. Safer too!
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Old 09-01-2010, 05:17 PM
 
 
 
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1987, 28l, 86, 87, blazer, bypass, chevy, fuel, fuse, jimmy, k5, location, pump, relay, s10


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