stuart69427

Yes you read that right Wayne!!!!!

My car has been running fine, only ran bad mon-wed last week :crossing-fingers: but yesterday, a couple times when I went to start the car, i slide the ignition into "on" but i didn't get a humm. wtf?

Ok so the realy is on the driver side firewall, there is two, which one is for the pump? Ok, i am sorry karl, but I don't know where all the fuses are, so are there more than just the one in the fuse box?

I bought a Vacuum/Fule Pump Pressure Guage from Pepboys a long time ago, but have yet to use it for its other function to test my pressure. Anybody have this guage and mind to tell me how to use it to test my fuel pressure?, cuase i can't find the manual. I can test vacuum with it no prob...

I have a new filter in there, well d@mn, i put that in in august, i quess it ain't so new, man time flies...

I had a new pump installed (not GM) in december... Last time i actually took it to a shop, my parents insisted that I have a "Professional" install it. Well he said my "Fuel Sending unit was clogged" but you guys assured me that, that was impossible to happen...

let me know what you guys think...

MDv6man

Well my 85 had the two relays and if I remember correctly the original fuel pump relay had yellow lettering on it. the other one had blue lettering. I don't know if that changed over the years though. the fuel pump gauge is easy -- unscrew the cap on the schrader valve, screw the pressure tester on (relieve pressure first), disable ignition coil, crank the motor. Were you getting any codes prior to this?

TomP

Oh, bummer, you can't use that gauge for the fuel pressure. That's a low pressure gauge, for use with a carbureted car. You'd need to grab the $40 one that goes up to 80 PSI with a high pressure hose. I found mine at Pep Boys, by Sunpro.

This chart might help you figure out the burned-up relay. I think our cars are close enough in years to have the same wires & relay locations:

-----------------------------------------------
DIAGNOSTIC CHART FOR CODE 54 (2.8L MPFI ENGINE)
---------------------------typed by Tom P------

Preliminary stuff:

Ignition off for ten seconds.
Ignition ON, listen for in-tank fuel pump
Fuel pump should run for 2 seconds after ignition on

Not ok? See "1"
Okay? See "6"



1. Ignition off. Remove the fuel pump relay, but keep the harness connected. This is
____located on the top of firewall, driver's side, on a relay bracket. It's the leftmost
____relay, with a connector that has these wires: Tan/white, black/white, green/white,
____orange, orange.

____With the relay still connected, back-probe terminal "A" (that's tan/white, circuit
____CKT #120) with a test light to ground, make sure you can see the test light from the
____driver's seat. Turn the Ignition to on (don't crank the engine/start the car). The
____light should turn on within 2 seconds.

____Light on? See "1A".
____Light off? See "2".

___1A: Repeat the test on CKT 120 (tan/white) at the rear body connector. You saw this
________connector if you replaced the fuel pump, it's in front of the tank, against the
________top of the underside of the car.

________Light on? Faulty pump ground or pump (ouch!)
________Light off? Fix the open (break) in circuit 120.



2. Disconnect the pump relay. Put the ignition on, engine stopped. Probe the fuel pump
____harness connector, terminal "E" (orange on the edge of the connector, Circuit 340)
____with a test light to ground.

____Light off? See "2A"
____Light on? See "3".

___2A: Repair open in CKT 340, this comes off of both your "computer-and-oil-pressure-
________safety-switch" setup and your "fuel-pump-and-computer-fuse".

________Your fuel pump/ECM fuse is under your hood, screwed down to the upper-frame-rail
________on the passenger side of the car, close to the air cleaner & black fuel-vapor-can.
________You'll see two little black boxes, each with two wires coming out of them, screwed
________down to the upper frame rail by one screw each. One of them has a red wire and an
________ORANGE wire coming out of it- that's your pump/ECM fuse holder. Pop the top off
________to see the fuse. (The holder with red & brown wires is for your MAF sensor.)

________Now, two things could happen here. You could have a bad fuel pump fuse- check the
________fuse. If it looks okay, replace it anyway... sometimes a fuse can look good, but
________really be blown. The second possibility- I want you to probe the red wire on the
________fuse holder with a test light to ground. The red wire goes to the positive-
________junction-block on the radiator support- your pump/ECM fuse might not be getting
________any power! If the light doesn't light, check the red wire hookup. However, with
________either case your computer would be acting up, too, and I don't think you could get
________the car to start at all.



3. Connect a test light beteween pump connector pin "B" (black/white wire, CKT450) and
____pin "E" (orange wire from step 2, CKT340).

____Light off? See "3A"
____Light on? See "4"

___3A: Repair open CKT 340. The black/white wire isn't making a good ground. Sorry, I
________don't know where this grounds out to. I'd imagine it goes to a screw on the car.



4. Connect test light between pump connector terminal "C" (dk green/white wire, CKT 465)
____and ground. Ignition to "off" for 10 seconds. Note test light within 2 seconds after
____ignition "on".

____Light on? See "4A"
____Light off? See "5"

___4A: Faulty Relay! Hey that's cool, a $10-$15 part from the GM dealer! But, if you
________replaced that already, something's funny. You might want to do the chart again.
________Note: The manual continues to test the "oil pressure safety switch", I'll put
________that test at the end of this message.



5. Ignition "off". Disconnect ECM A-B connector and check for an open, or a short to
____ground, in circuit 465- that's the dark green/white wire from the relay. It's on
____terminal "A1" of the ECM A-B connector.

____CKT 465 okay? See "5A"
____CKT 465 Bad? See "5B"

___5A: Check resistance across pump relay pins "opposite harness connector terminals B
________and C". Should measure 20 ohms or more to be good.
___________Resistance good? Faulty ECM A-1 connector, or bad ECM
___________Resistance bad? Replace Relay AND ECM.


___5B: Fix CKT 465. If CKT 465 was shorted to ground, re-check for a light "on"
________between harness connector terminal "C" and ground within 2 seconds after ignition
________"on".
___________Get a light? Cool, reconnect your relay
___________No light? Faulty ECM terminal "A1", or bad ECM.



6. Clear codes. Start engine and note service engine soon light. If the light comes
____on, check the code, if it's not 54 or you don't get a light, it's something else
____wrong, or an "intermittant" problem. But you get the code, so I shouldn't have
____even bothered typing this.



7. Backprobe ECM terminal "B2" (that's tan/white, CKT 120) with a test light to ground.
____Ignition off for 10 seconds. Note light within 2 seconds after ignition on.

____Light on? See 7A
____Light off? See 7B

___7A: Faulty ECM terminal "B2" or bad ECM.
___7B: Repair open circuit 120 to ECM terminal "B2".



*** Oil pressure switch test: Our 2.8's have two oil pressure switches. One is for the
gauge panel to control our oil pressure light (or gauge). The other one will keep the fuel
pump running if the relay happens to die while you're driving. I assume the theory was that
if you pull out onto a highway and the relay dies, you don't get killed? Anyway...

OP1. Start the engine, get it up to normal operating temperature. If you can, verify that
______the oil pressure is normal. Disconnect fuel pump relay- the motor should keep running.

______Engine stops? Bad oil pressure switch.
______Engine keeps going? See "OP2"

OP2. Reconnect fuel pump relay. Ignition "off". Find the fuel pump test terminal on the
______ALDL (Assembly Line Diagnostic Link, the connector above the driver's feet you used
______to get the error code out), which is terminal "G" -- the bottom leftmost terminal.
______Probe that terminal "G" with a test light to ground.

______Light off? No trouble found! (Doubtful, if you got this far & nothing's wrong...)
______Light on? Bad oil pressure switch. Oh yeah this switch is screwed into your engine
_________________block, right above your oil filter, with an orange and a tan/white wiring
_________________harness on it.



Whew.

-Tom P (Hot rodded 1986 Firebird 2.8l)

I Cant Drive 55

D a m n TomP , You must love to type. It would have taken me three hours to type all of that :rockon:
Oh BTW TomP Conrats on your engagement. Just let her know whos boss right off the bat. SHE IS!

stuart69427

wow, thats a lot of stuff, i just printed that and am going out to check all of that info out.

d@mn that sucks about the guage, oh well, live and learn, cuase i know what i am buying when i get back from PA...

KED85

This is what I've learned about those relays.
They always work in the end.
But it's one of the two side by side ones at driver side of firewall.
One on my 1985 is by the air inlet area/purge tank, also.
I usually go to auto store and "borrow" the large Time magazine sized Chiltons to find the suff I seek (location of parts/relays/vacuum lines).
The gas presure fitting is in back by distributor. Follow fuel rail.
Just turn on key, you'll see the answer.
If it's not above 40, oh-oh, sorry.
Mine was at 10lbs when I put that guage on it.
$hit.
THANK YOU AGAIN, DAN!!
But you already have newer fuel pump stuff?

stuart69427

Went to PA morning after i wrote this post, was going to run through all of tom's checklist there, but I haven't had this problem since then, well it didn't do it once yesterday no that i think about it, but that is it...

I will do the checklist when i get home for safety

FYI

Later, Stu
:lala:

Gumby

My fuel pump does not prime till the third time I turn my key. Could be cause of my lose colum, just have not had time to take it apart n tighen them screws. or who know but it has allways taken 2-3 turns of he key before my pump primes.


now if I had just driven the car it will start fine, just when it sits for a while, it wont start ill pump primes. other ime it must have enough fuel o start before it primes.

TomP

Can'tDrive55, I only had to type that once; It's saved on my computer. You can tell because it's so organized. If I had to type that from scratch, it'd be all over the place!

Stuart, glad to hear it's not acting up, but yeah, take a run through that test. It doesn't really take that long, and it's not that hard... I think all you need is a voltmeter and test light. That procedure is almost exactly out of the GM Service Manual, so it's the same procedure that a garage would be charging you $60 to run through. (Puts things in perspective, doesn't it?)

Gumby, if you ever find out what that problem is, let us know!

stuart69427

well I didn't get to check that yestereday, leaving for wrok now, so maybe tonight.

I am beggining to think its the keyhole cuase whenever i turn the car off latly, the radio is stayin on for like twenty seconds after the key is out of the hole and the keyhole is on the "off" position. If thats a seperate problem, there must be a short in the "accessory" circuit, cuase the radio keeps its memory so it can't be the "radio" circuit that feeds constant power.

Gumby

Tom I think the problem is I cant type.

I was stuck on my laptop for a week or so and man it sucked.
Both my coms ports craped out and I had no modem. MY new nifty USB modem arrived today.

I really dont know why but it take 2-3 turns of the key before my pump primes. Is there some default in the system; incase the pump dont work after a turn or two the computer bypasses it like a borg trying to save the hive.

These thirdgen computer systems are not too picky and do strange things.

TomP

Did you have a palm pilot plugged into one of the com ports? I hear some of the palms can fry an RS232 com port, and hooking a palm via a USB is safer.

The only default in the system is the "oil pressure safety switch". This does NOT kill the fuel pump if oil pressure drops to zero!!

By "safety switch", GM designed it in the circuit so if there is oil pressure, the switch bypasses the fuel pump relay, and keeps the fuel pump energized. This way, if you're driving around, and your fuel pump relay dies, your car keeps running. I think by you cranking the motor for 2-3 times, you're building up oil pressure, turning the safety switch on, and bypassing the relay.

Or, er, are you cranking the motor 2-3 times? Or just turning the key from "off" to "on", without cranking?

Gumby

I like external modems, they works much better than the newer win-modems that depend on your cpu for power.

Some reason com port 1 started craping out in win2k after the 4th so I moved it to com 2 but soon it was not working. I can hook the modem up to my laptop and it finds it and it works fine. Like my com ports died. In win me it will find it on com 2 but it will not work right with an RAS error and then it craps out. Thing the pors died some how.

I spent 20 bucks n got a USB one. Still external and USB works fine.


You know I have replaced my pump relay but the wires were very crunchy. like they had been hot n the connector was melted up some. But they were all there and it was only at the connector that it was like that. The AC one next to it was even worse. Real crispy.

That could be it and yes I do have to crank the motor over 3 time before she primes and then fires. Once in a while two will work.

stuart69427

I like the analogy!!!

I used my new digital multimeter that I ordered from sunpro.com's garage sale to run through the test.

See the crappy pic to see that about 3/4 inches of three of the four wires had missing insulation and the wires were crossing. I used electrical tape to cover them up for now.

I have a bad "Oil Pressure Safety Switch".

I still need to check the rear of circuit 120, but i now it SHOULD be fine since now, most of the time I can hear it prime, it was just occassionaly it wouldn't.

Also by ECM connector assembly does that mean on the ECM itself??? (I still need to do number #5) Conecter a-B ????

KED85

When were you the fly on my shoulder when I was shown the crossed wires at my junction block box....
I taped each wire, then taped the group of wires, keeping them separate.
I love as car that shuts off, now.
I think you found your problem.
AS IN, the wires shorting, take time to cool down and that accounts for the 1-2-3 tries of fuel pump effort.

I just got my digi meter, too. THANKS WAYNE!
Haven't used it, yet.
Probably will when I install the 3.4 into the Blazer this weekend.
Keep the 3.4 installtion 1985 Blazer "stock", problem solving tends to be "easier".

stuart69427

so far starts good ( less than a second to start :lala: :lala: :lala: )

Keeping my fingers crossed though. I will see if I can get a Oil Pressure Safety Switch at Pepboys tonight, cuase that could probable save me from stalling which happens a lot when the car was acting up, the wires probable shorted... and no safety switch to take over. It makes sense now. I just hope that the problem is comepletly solved for now.