Help-Intermittent Electrical Gremlin!!

jmendlik

Active Member
I'm having intermittent problem with my Fuel Pump prime circuit. I can go to start car and turn Key to on position and can here the fuel pumps prime for 2-3 seconds and go to start the car and no problem..fires right up. I can then turn the key off wait 2 mins or more ( like getting gas) and it will sometimes not prime itself again by going KOEO. When i don't here the pumps prime I know it wont start. This problem is intermittent like I said. Cold or Hot no difference so far.

Car is running Eric's ECUGN box/TR6/120lb INj and E85. The ECUGN also has LED lights to show POWER / WIDEBAND /FUEL PUMP/SPARK A / AUX


Here is what i observe when this happened this afternoon:
1. KOEO I have door chime/power to all guages, Check engine light is on but fuel pumps dont prime-i look at ECUGN and the fuel pump light went on so its getting the signal-also I have 12V power at pin A6 & C16 at factory connector.
2. I tried to start the car and it started and then died out--no fuel.
3. I tried to go KOEO again and same thing --no fuel pump prime-all lights show on as above .
4 Turn KOEO several times and no FP prime. Tried a few more times and then FP prime sometimes happens. Intermittent
4 When the FP prime does not occur I have gone and taken my jumper wires and touched the back of the alt to the grey wire for fuel pumps and they ran with this jumper on them. I then removed jumper and turned key off for 30 seconds or so and then went to KOEO and the pumps primed and car fired up!!
5. Ignition key tumbler does not feel sloppy-everything works on car when it does FP prime and startup and run without issues.




Here is what I have replaced so far:
1. New pass side FP relay -maybe a defective new part??? will be getting another just for the heck of things
2. Installed New Ignition switch. Rod looked fine. Neutral Safety switch operational
3. New IGN FUSE and ECM/INJ fuses
3. Verified orange wire at battery is good-no issues-- 12V at pin C16 at ECU Connector
4 Verified 12V ignition Pwr at pin A6 at ECU Connector.
5. When replaced Ignition switch all connectors looked like new-nothing burnt
6. all fusible links are intact-positive and negative battery cables are clean and tight.
7. all grounds at back of heads are on the Casper's ground stretcher kit.

I'm running out of patience-can anyone offer some tips or has anyone has this gremlin and figured it out?

I'm getting hesitant to drive the car long distances and shut it off and it wont restart!

Any help would be appreciated
 

ScottHeidinger

Active Member
Could be a fuel pump relay from what you’re saying but idk about the new GNECU...
Could be sending signal to pump relay but relay could have intermittent issue


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No disintegrations

Active Member
For an intermittent pump problem like this it might be worth it to run a semi permanent test light circuit back to the pump. So when it does it you will know for sure. Power at light but no prime equals bad pump for sure.
 

jmendlik

Active Member
Fuel pumps are arizonsGN superpumpers (Twin Dw300's) in the tank with billet sending unit and HD wiring harness with Hobbs switch on second pump. Fuel pumps run fine..just the prime cicuit..
 

MikeS

Active Member
Try adding some extra grounds? I had an intermittent fuel pump issue that I fixed by adding an extra ground to the frame back by the fuel pump harness, and a second ground from the same location all the way back to the battery. For a few bucks of wire it might be worth trying.
 

myfast70

Member
Joe,

First off, they are not Arizona GN pumps, Nick is one of my few resellers, they are innovativeparts.net pump ;)

So long as the power and grounds are hooked up to the alternator it's not a ground issue. Unless your engine to battery ground is bad but once again, if connected to the alternator the pumps will have all the power and ground they need.

I'll call you early tomorrow morning and will go over a few things with you. I have a 430am flight my time...
 

salvageV6

Daily Driver
The car should prime when the oil pressure gets over 4 psi. via cranking.

If that factory 3 wire oil pressure switch is removed or defective I'd fix that first you shouldn't get stuck ever unless the voltage output is intermittent to the pumps from the gray wire outward but you don't seem to think that could be the issue.

Then I would do the voltage test on the prime connector with a meter or test light as previously mentioned should light when the ECU sends out the signal.

You could also wire in temporary test lamps at the feed and output of the FP. relay switch the pink/blk wire and the gray wire, as well as the fuel pump relay trigger from the ECM which is the dark green wire.
 

captndave737

Well-Known Member
I'd check and clean all the connections in the system, bend the pins and make sure there's excellent contact. I once had my car towed 200 miles because the connector in my hotwire kit wasn't making good contact!! cleaned it, twisted the pins to make better contact and the problem was fixed.

I will say that 95% of every electrical problem I've had has been due to a bad connector. They may look fine but they're not. Corrosion that isn't visible to the naked eye can wreak havoc as can pins that have loosened from vibration. In 32 years i've only had a hanful of things go bad that couldn't be traced to a connector in the system. Especially with INTERMITTENT problems.

I was on my way home from RC's once and the car started acting up. Felt like a bad MAF sensor. Turned out the connector in the plug and play harness wasn't making good contact. bent the pins for better contact and drove away problem free. Cooling fans not working, connector pins, no high speed ac vent fan, connector pins etc.
 

jmendlik

Active Member
Will get out my test light and start probing connectors and wiring at the suggested locations and report back.

Also my 2nd new AC Delco Fuel Pump relay is due today.
 

scgnx2

Active Member
Will get out my test light and start probing connectors and wiring at the suggested locations and report back.

Also my 2nd new AC Delco Fuel Pump relay is due today.

A word of caution, when probing the female contacts be careful not to damage the contacts by inserting a larger probe than the original male pin. In all honesty, I would remove the female plug completely. Casper’s sells a fuel relay kit with pigtails. Just solder the new plug wires to the existing harness. I just went thru the same thing last fall. Just my 2 cents
 

jmendlik

Active Member
I got the Caspers replacement relay kit --just trying to figure out if it is my "new" relay that is defective.

Thanks for the heads up.

I did clean that connector with mineral spirits as it was pretty gummed up!

waiting for Amazon to drop off my new relay
 

jmendlik

Active Member
Problem Solved!!!

-That "New Autozone Relay" I was using was GARBAGE-Got my new replacement Relay and problem solved....

What a cluster-spent 2 hrs replacing and ignition switch that was not needed!!

Thank you to all who posted suggestions.

JM
 

TurboTGuy

Gray Beard Member
Thanks for posting the solution!

Too many times these threads die without the OP posting what he did, and what finally worked. Glad you got it worked out!
 
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