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HELP!!! Urgent!!fuel pump doesnt prime.. but runs...straight wire fuel pump??? by logical1
Started on: 03-01-2014 07:54 PM
Replies: 21 (722 views)
Last post by: Blacktree on 03-05-2014 10:41 AM
logical1
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Report this Post03-01-2014 07:54 PM Click Here to See the Profile for logical1Send a Private Message to logical1Edit/Delete MessageReply w/QuoteDirect Link to This Post
Its bigging the heck out of me. Ok been getting a lot of issues resolved just got my clutch back tight. Thanks to all for that.

Now to the big 1 this car is a pain in the a$$. A lot of wires wer spliced and cut for reason I dont understand nor will I ever bc po isnt around. It only starts by starting fluid (ether) once running its fine drives great. I noticed in center cention by eculm the tan wire which is fuel pump has an extra tan wire tapped and wrapped with a metal wire bracket to it. Def doesn't seem factory. When I tap wire and put it to a 12 volt source its working. Which I was consdering wiring to a button but it would get annoying have to hold a button down eveytime I get in the car, so is there a way to cut certain wires and run straight to the accesorry switch so when key is in the pump starts? Any help is grsatly appreciated.
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hookdonspeed
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Report this Post03-01-2014 08:36 PM Click Here to See the Profile for hookdonspeedClick Here to visit hookdonspeed's HomePageClick Here to Email hookdonspeedSend a Private Message to hookdonspeedEdit/Delete MessageReply w/QuoteDirect Link to This Post
you could always do this http://www.gmtuners.com/fiero/hot_wire.htm

its an upgrade over factory, and would "Cut out" any of the hack jobed circuits someone else messed with.
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logical1
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Report this Post03-01-2014 09:11 PM Click Here to See the Profile for logical1Send a Private Message to logical1Edit/Delete MessageReply w/QuoteDirect Link to This Post
Yea b4 I posted I searched and saw that. Just looked really confusing. Plus ive got an 88 . 2.5 -5- speed, and when I look I didnt see the same setip in mines. Anyknowhow of a simple method that would b easier or atleast a breakdownnof that method rhat would apply to my year. Also will that rework the prime feature.l?
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logical1
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Report this Post03-02-2014 12:59 AM Click Here to See the Profile for logical1Send a Private Message to logical1Edit/Delete MessageReply w/QuoteDirect Link to This Post
I see the wire goes into the plug, then enters into the fire wall. Could I just clip wire off of fuel pump and then run an 8 guage wire to it? Does the ecm need to read anything off fuel pump? Anybody have anykind of idea?
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Bloozberry
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Report this Post03-02-2014 07:39 AM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
First make sure the fuel pump relay is working. You can do that by finding it on the firewall behind the driver's seat in the engine compartment near the top. There may be more than one relay there so to identify which one is the F/P relay, locate the one with the following wires: 2 orn/blk, tan/wht, grn/wht, and blk/wht. Use a jumper and apply 12V to the grn/wht wire... if the relay doesn't click and start the pump, then replace the relay and try it again. If it does work by jumping it there, then there's likely a break in the green/wht wire between the relay and ECM pin 24 on connector C2. Try jumping between those two points and seeing if the pump primes as it should when the ignition is turned on.

If that fails, then check to make sure that ground G504 is still good (a big eyelet with 2 blk/wht wires running to it and attached to the top LH front of the engine above the starter solenoid). The wires have a habit of breaking off from that point. If all else fails, then you could clip the grn/wht wire at the ECM, and splice a new wire to the end that goes to the relay. The other end of the new wire can be plugged into one of the two little outlets on the fuse panel marked IGN. You should find those outlets at the bottom left corner once you swing the panel down. They'll accept a simple bayonet-style connector, the type you can buy at any parts store that you crimp onto the end of the wire.

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Blacktree
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Report this Post03-02-2014 08:49 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
^ what he said

And if the fuel pump relay is missing (i.e. hacked up wiring), you should re-install it, and any necessary wiring.
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logical1
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Report this Post03-02-2014 01:04 PM Click Here to See the Profile for logical1Send a Private Message to logical1Edit/Delete MessageReply w/QuoteDirect Link to This Post
Ok followed every step and no luck with power to the grewn wire even went and replaced relay. Nothing. So I was going to do the ecm wiring and I was looking for the wire that I splice to ign and I realize that the other green/white wire is snipped sooo small its inside the connector. The main wire from the e is fine its just that second green and white wire in the same pin connection thats the problem. How do I work around that? Im about to post a picture. Unless this wire isnt nesessay, but I feel it has to be bc only 1 green and white wire is comming out of top black ecm harness. If not where does ign wire go.

Ughhhhhh I hate the po for this shhhittttt.... I feel like riping my hair out!!!!

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logical1
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Report this Post03-02-2014 01:25 PM Click Here to See the Profile for logical1Send a Private Message to logical1Edit/Delete MessageReply w/QuoteDirect Link to This Post
Also I notice there are two tan/ white wires coming from the same above harness (top right) they both splice Into 1lower tan/white wire. Doesnt look stock very jerry rigged 2 down to that 1 tan/wht wire in center console I splice in ro botrom wire and supplied power and pump worked. Are one of thoses upper tan and white suppose to go to a 12v ign instead of plugging intow that single wire?
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Bloozberry
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Report this Post03-02-2014 02:05 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
There should only be a total of two green/white wires going to the ECM and both should be going to different pins on different connectors. One of the green/white wires goes to pin 21 (fourth from the end of one connector). That wire controls the coolant fan relay. The other green/white wire should go to pin 24 of the other ECM connector (last hole on one end). That's the one that controls the fuel pump relay. If it's snipped (like it looks to be in your photo above) then that's why it's not working properly.

To reconnect it even though it's too short in the cabin, you can always try finding the wire in the bundle in the engine bay, snipping it there, and splicing an extension to it so it can reach the ECM back in the cabin. You'll have to drill a small hole through the side of the firewall plug (where all the other wires go through) and thread the wire back into the cabin that way because you'll never get it back through with the rest of the wires. Then if you're worried, you can always put a dab of silicone caulking on the hole with the wire.
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Blacktree
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Report this Post03-02-2014 02:38 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
You can also detach the wiring pass-through from the firewall, and pry the two halves apart. You just have to be careful not to break the plastic while you're prying it apart. It can be a pain. But once you get the two halves pulled apart, you can get at that snipped wire to splice it. Then you put the pass-through back together, and plug it back into the firewall.

If you don't feel comfortable with that, then I'd suggest drilling a hole in the firewall like Blooz said. And to be honest, drilling a hole will probably be quicker and easier.
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logical1
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Report this Post03-02-2014 04:03 PM Click Here to See the Profile for logical1Send a Private Message to logical1Edit/Delete MessageReply w/QuoteDirect Link to This Post
So if I have connect that green/white wire thats snipped to give power to relay. Thenb y is it when I splice the green/white at relay and touch the battery it doesn't make relay come on. I swapped relays and even bought a new 1. Am I missing something? I dont see how if 12v power from battery to relay green/white wont make it prime how hacking into the ecm wires will..??

Here are the fuel pump wires that are hacked. I touched 12v to them and pump cut on. Seems like maybe one of the upper two should go somewhere elese.... is that y the green/wht isnt working when its powered??



Ugggghhhhh im going crazyyyyyyy!!!!!
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Blacktree
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Report this Post03-02-2014 04:24 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Actually, that appears to be a factory splice on the beige / white wires.

BTW, did you also verify that the black / white wire is grounded? It needs a good ground, or the relay won't click.

[This message has been edited by Blacktree (edited 03-02-2014).]

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logical1
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Report this Post03-02-2014 07:49 PM Click Here to See the Profile for logical1Send a Private Message to logical1Edit/Delete MessageReply w/QuoteDirect Link to This Post
Yea black/white wire was really solid, not frayed at all.... wow I didnt know they did a factory splice.. im still stumped as far as understanding is concerned. I just dont see how the green ecm wire when ran will power the relay if touching the green wire on relay to a power source doesnt? I will do it but, im having a if some1 tells you to jump off a bridge moment... I just knoq how sensitive the ecm can be and in my area there are no other fieros in junk yard to salvage a ecm from if it goes wrong..

Maybe avoiding the relay circut is the only way. Im reading it now and when it says on cabin side is that the tany and white single wire b4 it splices? Im sorry the wording is just loosing. Me I really need it like lame'mans terms step by step and wire location...?... please someone help me
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Blacktree
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Report this Post03-02-2014 09:27 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Did you actually test the ground wire with a multimeter or a test light?
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logical1
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Report this Post03-02-2014 10:53 PM Click Here to See the Profile for logical1Send a Private Message to logical1Edit/Delete MessageReply w/QuoteDirect Link to This Post
No I didnt I have a multimeter I bought from harbor freight. I know how to test for positive but how do I test for a ground. I know same principles apply get fresh wire but what numbers do I look for? And how do I...? I know ground first to check for power so how do I check for ground....?
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Blacktree
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Report this Post03-02-2014 11:24 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
The easiest method is probably to check resistance (ohms) between the black/white wire and the chassis. Ideally, the resistance should be zero, or close to it. If resistance is infinite, you have a bad ground.
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logical1
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Report this Post03-03-2014 01:13 PM Click Here to See the Profile for logical1Send a Private Message to logical1Edit/Delete MessageReply w/QuoteDirect Link to This Post
Ok so ground looks goos on volt meter. 1 wire the other floats a little on multimeter I spliced with a ground and cut switch on got nothing so I spliced ground again and this time added a splice on green wire with a power and relay cuts on!!!!!!!

So seeing as the green wire doesnt get power on its on. Both plugs on ecm white-plug- &black plug green and white wires are going into the big bundle of wires into the cabin neither are snipped... sooo I wondering which needs to go to the relay white plug or black plug OR do I just snip the green wire on relay and lett ign give it power? Im trying to understand the previous post about how to run the wires, but its loosing me. Plus I dont know how to count pins or know the connector names so it sounds like a foriegn language to me...

Now please rember whith either the car runs and drives , which is crazy bc something is making the fuel pump run when either starts car. I just dont want to be sending too much power to the fuel pump and create a hot circut that might start a fire... or am I just being paranoid?
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Blacktree
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Report this Post03-03-2014 09:54 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
The car still runs because the oil pressure sender is turning on the fuel pump. It's designed to do that, in case the relay dies.

The green / white wire on the relay should connect to the ECM. That way, the ECM can turn on the fuel pump. Like Blooz said above, you're looking for a green / white wire coming from pin #24 on the ECM electrical plug. The numbers are stamped into the side of the plug. So just look for the little number 24 with a green / white wire next to it.
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logical1
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Report this Post03-03-2014 11:41 PM Click Here to See the Profile for logical1Send a Private Message to logical1Edit/Delete MessageReply w/QuoteDirect Link to This Post
Ok, cool green and white ecm snipped and by pass to the relay and splice in a new solid ground.. Huge help I know ive been a bit of a panty waste when it comes to this its just on 1 hand I dont want to start a fire n on other didnt want to fry ecm. Thanks again I look on ecm plug for the 24 wire im guessing it will be that wire beside the snipped 1.

Id like a pin out for 88 2.5 /5speed bc the white/blk stripe on black ecm connector is snipped and below that an orange wire is snipped. This po was a p.o.s..uggghhh I hate ppl like that.
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Report this Post03-05-2014 04:58 AM Click Here to See the Profile for fierohohoClick Here to Email fierohohoSend a Private Message to fierohohoEdit/Delete MessageReply w/QuoteDirect Link to This Post
Just to clarify, the ECM does not supply 12V+, what it does is supply the ground for the circuit.

Sorry if that has already been mentioned, I just skimmed the thread and didn't see it anywhere.

------------------

Where will the road take you today?

Some helpful links I've done
How to remove inner door panels, with pics.
How to remove outer door panels, with pics.
How to make rear coil-overs using factory struts, with pics.
How to remove rear bearing hubs, with pics.
How to modify the stock Fiero radio for MP3 players, with pics.
How to come up with the right coolant hoses for that engine swap...With Pics.
Basic Fiero electrical testing "How To" and equipment...with pics.

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Report this Post03-05-2014 07:27 AM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierohoho:

Just to clarify, the ECM does not supply 12V+, what it does is supply the ground for the circuit.

Sorry if that has already been mentioned, I just skimmed the thread and didn't see it anywhere.



Correct for all the other outputs of the ECM EXCEPT the fuel pump relay. GM has the ECM supplying +12v on the Dk. Green/White wire to activate the relay. Beats me as to why. Thus the other wire of the relay coil should be Black or Black/White and should run to ground.

[This message has been edited by phonedawgz (edited 03-05-2014).]

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Report this Post03-05-2014 10:41 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yeah, I originally thought the ECM grounded the relay, until I looked up the electrical schematics. The funny thing is there's another dark green wire with a white stripe in the engine wiring harness, and that one's the ground for the radiator fan relay. Why GM decided to use the same color for a power wire on one circuit and a ground on another circuit completely escapes me.
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