Rusty Bowtie
General Category => General Discussion - Intros => Topic started by: munch on March 28, 2022, 11:53:51 AM
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I have a 2001 Chevy 5.3 in my 1953 Chevy 3100. Recently I swapped the stock intake for a Jegs fabricated LS intake manifold #555-513050 and external filter/regulator #555-14410. I prime it then start and it tries to run, but then seems to run out of gas. It does this repeatedly.
I am told that because I no longer have a fuel return at the manifold, and instead have the return line at the regulator, that I need to get a retune for the computer to compensate for the returnlesss manifold.
Does this sound right?
Thanks guys...
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When I was messing with the megasquirt I built the engine would start and run on the start circuit but as soon as I let the key return to the on/run position it would die. It would run as long as the starter was circuit was on, sorta' tough on starters. I was getting no fuel signal except in the start position. I don't know if this has anything to do with your issue.
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When I was messing with the megasquirt I built the engine would start and run on the start circuit but as soon as I let the key return to the on/run position it would die. It would run as long as the starter was circuit was on, sorta' tough on starters. I was getting no fuel signal except in the start position. I don't know if this has anything to do with your issue.
Good info, thanks Sixball...
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Do you have fuel pressure gauge? If so hook it up and check fuel pressure at the shrader valve....should be in the 40-50 lb range If it's a lot higher (because of no fuel pressure regulator return line) the injectors may not be opening. I had a similar problem with my son's 37 Chevy after installing a LT1 EFI driveline, one of his buddies bent the return line and the fuel pressure went up to about 90-110lbs PSI..the 24lb injectors injectors could not open under that pressure.
Oh yeah...if the MAF sensor is on backwards..it will start and shut off. If your LS harness has an OBD2 connector...try reading codes.
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Maybe this could help.
https://youtu.be/OMUlvsy7wUk
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Do you have fuel pressure gauge? If so hook it up and check fuel pressure at the shrader valve....should be in the 40-50 lb range If it's a lot higher (because of no fuel pressure regulator return line) the injectors may not be opening. I had a similar problem with my son's 37 Chevy after installing a LT1 EFI driveline, one of his buddies bent the return line and the fuel pressure went up to about 90-110lbs PSI..the 24lb injectors injectors could not open under that pressure.
Oh yeah...if the MAF sensor is on backwards..it will start and shut off. If your LS harness has an OBD2 connector...try reading codes.
The pressure at the fuel rail is 58 lbs which is what the suggested regulator calls for. The MAF sensor is correct. The only code is P0650. Thanks EDNY
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Maybe hook up a noid light to insure the injectors are getting power while cranking, watch the fuel pressure after you prime it and it starts temporarily....to see if it spikes.
On a side note just last week my 1994 dually truck with TPI wouldn't keep running...I ohm'd the injectors and located (3) bad ones. Replaced all 8 and the truck runs like a beast again.
Have no experience with those self regulated fuel filters....but it seems that there is a fuel issue if everything worked before the swap?
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Maybe hook up a noid light to insure the injectors are getting power while cranking, watch the fuel pressure after you prime it and it starts temporarily....to see if it spikes.
On a side note just last week my 1994 dually truck with TPI wouldn't keep running...I ohm'd the injectors and located (3) bad ones. Replaced all 8 and the truck runs like a beast again.
Have no experience with those self regulated fuel filters....but it seems that there is a fuel issue if everything worked before the swap?
Not sure I understand the noid light suggestion. The fuel pressure stays at 58 lbs when it cranks and stays there even after it dies. The injectors are all new.
So you don't think the retune is a option?
Thanks EDNY
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The noid lights are basically test lights that plug into the injector connector. If the injectors are getting a pulse they light up.
Harbor Freight sells them:
https://www.harborfreight.com/search?q=noid%20lights
As far as a tune if you have the same PCM it should start and run...a tune would be required to optimize the new intake flow etc. Your current PCM must have had VATS tuned out ? because the condition resembles a VATS problem.
If your the new injectors are the same as the old ones (lbs and flow rate)..the old tune should work to get it running. Sounds like if you spray starting fluid into the throttle body it starts?
Do you have good spark?
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The noid lights are basically test lights that plug into the injector connector. If the injectors are getting a pulse they light up.
Harbor Freight sells them:
https://www.harborfreight.com/search?q=noid%20lights
As far as a tune if you have the same PCM it should start and run...a tune would be required to optimize the new intake flow etc. Your current PCM must have had VATS tuned out ? because the condition resembles a VATS problem.
If your the new injectors are the same as the old ones (lbs and flow rate)..the old tune should work to get it running. Sounds like if you spray starting fluid into the throttle body it starts?
Do you have good spark?
Yes after letting the fuel pump prime it to the 58 lbs it does start but doesn't run long. It seems to run out of fuel although the pressure is still 58 lbs.
The new intake uses a map sensor 555-14538 which says it is for a 2009-2015 LS 6.2 and not a 2001 5.3 as I have. It has an adaptor cable p/n ls1-ls3 map adapt. to match my harness connector. I tried to use the old map sensor, but the plug in port is larger on the new intake.
Yes it has spark. I should have titled this post "Starts but does not continue to run," Sorry I was misleading.
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I would concentrate on the MAP sensor..maybe try a temp wiring with test leads? The MAP controls timing and injector pulse rate....that's where the tune would come in. I'm not up on it..but MAP sensors come in 2 and 3 bar configurations....with wrong bar rating ....car starts but won't continue to run.
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Here's a write up on GM MAP sensors....it has the old style MAP sensors...you are most likely using the newer/smaller sensor?...maybe this info might help ID which BAR sensors you have...if the old and new MAP sensors have different BAR ratings I suspect that will be your problem!
https://www.robietherobot.com/storm/mapsensor.htm
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Here's a write up on GM MAP sensors....it has the old style MAP sensors...you are most likely using the newer/smaller sensor?...maybe this info might help ID which BAR sensors you have...if the old and new MAP sensors have different BAR ratings I suspect that will be your problem!
https://www.robietherobot.com/storm/mapsensor.htm
Ed, my research shows that the map sensor that Jegs suggested for their intake is a 3 bar. I believe the stock 2001 5.3 map sensor is a 1 bar, but I cannot find proof. I cannot test my old sensor because it is too small for the intake's map port.
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10-4...I think have you the problem narrowed down. Maybe some rubber hose/tape to make it fit? If I can help I have a bunch of the old style 1Bar sensors.
From that link above:
1 Bar MAP sensors are used on NA(naturally asperated) vehicles.
2 Bar MAP Sensors are used on forced induction vehicles(Turbo & Supercharged). They can measure up to 2x the apmospheric pressure(29.4psi), so that means it can measure up to 14.7psi boost(the atmosphere is 14.7psi + 14.7psi from the turbo/supercharger).
3 Bar MAP sensors can measure up to 44.1psi, which translates to 29.7psi boost from a Turbo/supercharger.
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10-4...I think have you the problem narrowed down. Maybe some rubber hose/tape to make it fit? If I can help I have a bunch of the old style 1Bar sensors.
Thanks Ed, your hunch about the map sensor was right on. Called Jegs and explained the map sensor and after much research the tech found one in the 1 bar range that would fit the intake. He gave me a Delco number and I got it at the local parts store. Fired right up...
Thank you sir...
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Great - I like it!
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COOL! This has been interesting, Glad you got it running.
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Glad you solved it!