5.3 swapped OBS fueling issues possibly wiring related HELP

[AaronP]

Hello all,

I hope someone here can help me I am in a bind. I have a 5.3 swapped 95 Silverado. I reworked my harness according to lt1swap.com and made my own fuse/relay box following the direction of the website. I seem to be having likely a voltage issue that I need to diagnose. (Side note; the website said that the wires that came with the kits he linked to should not be used as they aren't designed for the application but I didn't replace them... thinking they should suffice.)

When I turn the key to auxiliary position the ECM is supposed to send voltage to the fuel pump for 2 seconds. When I took a test light to the relay it merely blipped for a split second. I have several harness grounds and the ground for the fuse/relay box tied into the bracket that holds the alternator. Does anyone know if the fuse/relay box needs a dedicated ground or if perhaps by not using a different wiring that the fuse/relay box is not going to receive enough voltage to work properly? I am stumped.

If I crank on it for a good 30 seconds I will have fuel up to the fuel regulator but it does not seem to cross over to the relief valve on the rail, that or it doesn't hold pressure... when I push the pin in it there is no fuel there. I'm thinking this is just because of the continued crank that brings fuel up but doesn't hold the pressure without proper voltage?

I know this is a little obtuse but some direction would be greatly appreciated. Can someone who has reworked their harness/built a fuse/relay box following lt1swaps guide please chime in? I have an outdated multi-meter which makes diagnosis difficult for me.

Another note: this is just after I had deleted the VATS and Column Lock Security from the tune and changed nothing else. Before I did this it would fire for a split second and then die because of the VATS... would the Column Lock delete keep from fuel delivery?

I really would like to get this thing to move forward and backwards at least before snow falls in a month or so, sorry for the long query. Please someone help me.

(I will try to supply some photos when I get home to help illustrate.)

 

[sewlow]

You might have better luck getting the info you require here.

https://www.facebook.com/groups/607787819352393/

 

[RDF1]

What I would do to trouble shoot this issue.

Jump out the fuel pump relay. Easiest way is to pull the relay. Insert a wire from pin 30 to pin 87. Pump will run until you remove the jumper wire.
Check fuel pressure. If your not getting about 55psi then you have to look elsewhere. Maybe clogged filter, weak pump, something along those lines.

Sent from my HiDiNg PlAcE

 

[AaronP]

Thanks for your reply. I have jumped it and attempted to start while its jumped but it wont fire. Perhaps the injectors arent firing or theres no spark... but it's not feeding by itself so I'm thinking the fuse box is the issue or the tune at this point

 

[RDF1]

I would suspect you have a ground issue.
I'd have to reroute the grounds to the rear of the block and rear of the head where they are from the factory.
Also check and make sure with the key on / engine off that you have 12 volts at the injectors and coil packs.
Also make sure your pcm still has power as your trying to crank the engine from the key.


Sent from my HiDiNg PlAcE

 

[blacksport]

i did the swap in my truck. i used the fuel pump trigger wire from the 411 ecm taped it into the the relay and kept the factory fuel pump relay and wiring. i was just saying the other day if i did it again i would not do my own harness.you can do it with 3 wires and keep the fuse block.

xc_hide_links_from_guests_guests_error_hide_media

 

[RDF1]

i did the swap in my truck. i used the fuel pump trigger wire from the 411 ecm taped it into the the relay and kept the factory fuel pump relay and wiring. i was just saying the other day if i did it again i would not do my own harness.you can do it with 3 wires and keep the fuse block.

xc_hide_links_from_guests_guests_error_hide_media

I've done it that way and the whole rewire way. I do like how clean of a install the whole rewire is. But now after messing with the Holley terminator x max setups on a turbo car and a truck. I'll be using them more.


Sent from my HiDiNg PlAcE

 

[blacksport]

are you running the stock 5.3 intake or a holly?

 

[RDF1]

are you running the stock 5.3 intake or a holly?

If your referring to me...
I'm runnin all stock truck stuff on my 5.3.

Sent from my HiDiNg PlAcE

 

[Dropped88]

You mentioned you jumped it but you never mentioned if pump ran or what psi