No Fuel Pressure

NoVA_87_GN

Member
Hoping to get some help here. Went out to start car this morning, noticed when I turned my key to start position the external fuel pump didn't kick on, turned the car over, no start. been. Here's my setup, holley external fuel pump and hotwire kit. Here's what I've done so far:
-Checked battery, it was low, auto parts store charged it up, and I'm good now
-Checked power at alternator post, got 12v
-check fuse on hotwire kit in engine bay (40a) looks fine.
-check fuel pump relay (passenger side finder), pnk/blk wire has 12v, jumpered pnk/blk and gray wire to bypass relay, still wouldn't start
-tried checking the hotwire kit wires in the back, don't really see any voltage anywhere (12v) which i would have expected to

I'm hoping its not the fuel pump as it looks like 600 bucks if I wanted to replace it with another similar one. Hopefully someone can help me with what i might be missing or what i might be measuring with multimeter in the rear of the car.
 

TexasT

Texas, Where are you from
Some reason you decided to do an external fuel pump? Plenty of options for a good In tank depending on how fast you Intend to go. Those external are good at pushing but pulling isn't near as good for them and if it lost prime it could over heat as the fuel going through it is also used for cooling the pump.
I think I would jump a hot wire right to the pump to see if it will spin. Careful as jay Leno took some gas to the face and from what I've read is healing up from burns.
 

Chuck Leeper

Toxic old bastard
Staff member
First, find out why there's no power there, even with the relay jumped out.

"check fuse on hotwire kit in engine bay (40a) looks fine".
If you didn't test it, you've not verified it's good.
If you don't have power in the back, the pump being toast has no bearing on the "no start" issue.
 

salvageV6

Daily Driver
You need to check the hot wire relay which is part of the "hotwire kit" that is triggered by the stock fuel system relay power. That needs to send the power out to the fuel pump when triggered by the factory wiring.
 

NoVA_87_GN

Member
@TexasT external fuel pump was on the car when I purchased it. it's also got a sump tank, if i have to replace pump, i might swap out to a stock style fuel tank with an internal fuel pump set up.

@Chuck Leeper Yeah, I'll have to dig in there today and pull that fuse and check it, am i just running a continuity check on my multimeter to make sure the fuse is good?

@salvageV6 Agreed, can't figure out why i'm not getting any power when I test the connections in the back. No voltage on what I would assume were the "hot" wires coming from the front of the car.

Side note, a week or so ago, i went out to take the trash out, noticed a humming coming from the back of the car, fuel pump was running, but car was not on, no key, just sitting there (first time it'd ever happened). I pulled the connection, let it sit for a bit, plugged the connection back in, started the car up a few time no issues. Pulled the connection just to be safe while it sat, that's when i plugged the connection yesterday and tried to start it up with no luck. If it ran a week ago after that incident, not sure why it wouldn't run now. Thanks for the help.
 

dynoman

Well-Known Member
Sounds like the hotwire relay hanging up / burned contacts . We would get this issue all the time at work on vibration welders with relays that were actuated under load , the contacts would burn and hang up . It happened so often that I carried a set in my tool box all the time .
 

Chuck Leeper

Toxic old bastard
Staff member
@Chuck Leeper Yeah, I'll have to dig in there today and pull that fuse and check it, am i just running a continuity check on my multimeter to make sure the fuse is good?
I'd check the wiring on the sides of the fuse first. Power in and out with fuse in place?
If not pull the fuse and check it. Look at the fuse holder sockets. Nasty?
Keep in mind that the relay must be in good condition and jumped closed. Trying to check with just the short prime cycle won't work well.
 

salvageV6

Daily Driver
Post a picture of the "connections in the back".
You need to find the hotwire relay and check that is has a ground on one side of the coil and the +12 trigger power on the other from the factory system either jumped or in prime mode key on.
The heavy fuse wire should go to one of the relay output contacts and the fuel pump hot wire to the other normally open relay switched contact.
The hot wire kit relay can be located out front or out back depending upon the kit. It can also be easily home made and located anywhere including near the new fuel pump location.
After verifying the fuse in and out +12 as Chuck mentioned trace that heavy (usually red) wire and find the hot wire kit relay and test there.
 

NoVA_87_GN

Member
@salvageV6 here's a few pics of what i believe is my hotwire kit relay towards the rear of the hotwire kit. this what I am looking for? ..

@Chuck Leeper I'll check those connections after work today.

thanks for al the help, i'm learning as i go.
 

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salvageV6

Daily Driver
That looks like it may be it. There's even a diagram on it to show you where the contacts and coil are by number.
The fat red wire should have power on it all the time through the 40A hot wire fuse you hopefully checked out by now. Have to unwrap the tape to check the other wiring on there like I previously described.
If that brown wire is the ground to the relay coil make sure its a good connection to the metal it's bolted to that looks a bit suspicious.
 

dynoman

Well-Known Member
You can partially pull the connector off just enough to get meter leads onto the relay posts . Also if you jump the stock relay to bypass the 4 second prime , tap on the hotwire relay with a screwdriver handle and see if the pump turns on . If it does replace the relay .
 

scgnx2

Active Member
That particular relay is probably not a weather sealed version, hence the electrical tape. Having that mounted under the back of the car is less than ideal. Unplug it and look at the contacts for corrosion. Most Hotwire kits I’ve seen mount the relay under the hood.
 

NoVA_87_GN

Member
So did some more troubleshooting when I got home. Tested the wiring on both sides of the fuse in the engine, 12v on both wires, tested the fuse for continuity, tested good. followed hotwire kit to the rear to make sure everything looked good, it did. tested that fat red wire and got 11v-12v, but wasn't getting voltage through the relay. ran a jumper from fat red wire connection to the wire running to fuel pump for a quick second and heard the fuel pump start up. fuel pump appears to be good and the relay is bad. any ideas on where I could get a replacement for that particular relay?
 

TexasT

Texas, Where are you from
Looks like this one I think. Might put those numbers into a google search and see what you can come with .
I have one of these Chinese relay tester things. About $15 I think but pretty nifty when you need one.
Not sure why it sez robat or human but that is the link to one like what I have. Cheap yes, but seems to weed out the bad ones.
 

NoVA_87_GN

Member
I picked up a few of these off of eBay:


I looked at the other site but I had to spend more than 50 bucks to shop there. Only thing I noticed on the ones I ordered was the amps were 40/30, where as the relay I pulled off the car is 50/40 amp. Think that’ll be an issue?
 

salvageV6

Daily Driver
You need to know the specs. of the pump that is in the car to tell for sure.
The 40 A rating is usually the N/O contact, should check that with the specs. to be sure, which is the contact you will be using.
Note: You mentioned the fuse rating is 40A so the 40A relay contact should be okay as well if the fuse has never blown with it. Just verify the N/O contact will hold 40A.
 

NoVA_87_GN

Member
Looking at the specs for the pump, it says the max amp drawn is 38A, so with it being a 40A rating on the N/O, I should be good right?
 

dynoman

Well-Known Member

Mr.Spool

Well-Known Member
Some reason you decided to do an external fuel pump? Plenty of options for a good In tank depending on how fast you Intend to go. Those external are good at pushing but pulling isn't near as good for them and if it lost prime it could over heat as the fuel going through it is also used for cooling the pump.
I think I would jump a hot wire right to the pump to see if it will spin. Careful as jay Leno took some gas to the face and from what I've read is healing up from burns.
Not so with the new brushless spur pumps from aeromotive they have been the real game changer.
I could on and on but you dont need to volt them down to run them and they actually perform and last with alchohol based fuels.
They can also be run on a stock ecm or aftermarket and can be in tank or external
I run external personally.
I have seen sooooo many in tank pumps fail and pulled too many out and watch fuel pressure die off upstairs where these cars need it.
if you run multiple you can never tell if one is going away,and many times till it's too late.
I've had nothing but incredible results on the brushless spur and that's all I will run on my cars now and no I'm not sponsored 😁
 
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