Fuel system help.... maybe

[crammit442]

I've done a bunch of searching and haven't found anything that sounds exactly like my situation. I got my '99 2wd 5.7 l from my grandmother when she passed away a few years ago. It initially ran fairly well, but was really only used to occasionally pull a lawn trailer. A year or two ago it became hard to start. The battery is strong, but if hasn't been started in a day or two it needs a squirt of starting fluid/fuel for the first start of the day. Once it starts it restarts fine until it's put away for a few days. The fuel pump relay tested good, but I replaced it anyway for good measure. I also replaced the fuel filter. I can hear the fuel pump cycle when the key is turned on. This hasn't been ideal, but I'm the only person that drives it and not very often so I've just lived with it this way. As of last weekend, it will start with a prime, but will only run for a few seconds. I replaced the fuel pump today (lots of fun) since I've seen people say their pump runs, but isn't delivering good pressure. I now have great fuel pressure, but it still only runs briefly. I can hear the system prime when the key is turned on and it will briefly run well, but falls on it's face and dies after a few seconds. I'm really a 3rd generation 4Runner guy and am not very Tahoe savvy. I'm not throwing in the towel, but I'm fresh out of good ideas. Thanks in advance for any suggestions.
Charles

 

[exp500]

You need some cheap and generic tools to find/fix 95% of the normal problems.
Spark tester, Fuel pressure guage, multimeter, test light, bluetooth scanner. Maybe $100. for all.
As a guess, I would first point to distributor cap. But it likely needs a full tune up. Plugs, wires cap/rotor, air cleaner.

 

[iamdub]

I've done a bunch of searching and haven't found anything that sounds exactly like my situation. I got my '99 2wd 5.7 l from my grandmother when she passed away a few years ago. It initially ran fairly well, but was really only used to occasionally pull a lawn trailer. A year or two ago it became hard to start. The battery is strong, but if hasn't been started in a day or two it needs a squirt of starting fluid/fuel for the first start of the day. Once it starts it restarts fine until it's put away for a few days. The fuel pump relay tested good, but I replaced it anyway for good measure. I also replaced the fuel filter. I can hear the fuel pump cycle when the key is turned on. This hasn't been ideal, but I'm the only person that drives it and not very often so I've just lived with it this way. As of last weekend, it will start with a prime, but will only run for a few seconds. I replaced the fuel pump today (lots of fun) since I've seen people say their pump runs, but isn't delivering good pressure. I now have great fuel pressure, but it still only runs briefly. I can hear the system prime when the key is turned on and it will briefly run well, but falls on it's face and dies after a few seconds. I'm really a 3rd generation 4Runner guy and am not very Tahoe savvy. I'm not throwing in the towel, but I'm fresh out of good ideas. Thanks in advance for any suggestions.
Charles

I agree with what @exp500 said. To expand on the scanner, get one that'll show the live data from the sensors. You might have one that's far out of range and the ECM is just responding as programmed. For example: I had a '91 Blazer that got terrible mileage and kept fouling O2 sensors and, eventually, plugged the cat. Punching out the cat and replacing the O2 sensor ever so often kept it on the road. I was very young and didn't know any better. I worked at a mechanic shop, but, I was just a tire and lube monkey. Anyway, they let me try out their scan tool and I found the coolant temp sensor to be reporting some impossible temperature far below zero. It was keeping the engine constantly in warm-up mode. The ECM didn't know there was a problem and was just reacting accordingly.

I'm wondering if yours runs fine in open loop when the ECM is ignoring input from a few sensors and running on a base map. But, when it goes into closed loop, it then reacts to the erroneous input from a faulty sensor and alters the timing and/or fueling and dies.

Firing right up from a cold start then sputtering and dying after only a few seconds sounds like it's flooding itself. You might have a faulty injector (spider assembly) or leaking regulator. Have you tested the fuel pressure since installing the new pump? Aside from engine running pressure, you need to test the leak-down characteristics.

 

[exp500]

BAFX is a decent cheap one.

 

[crammit442]

Thanks for the responses. I have access to a cheap "Kobra" Bluetooth scanner, but I doubt it has anything more than the most basic features. As far as reading live sensor data, will there even be any data to read if it only runs 3-4 seconds at a time? I don't know if the BAFX Bluetooth scanner mentioned below will give live data or not. If not, any suggestions for a budget friendly scanner that will? I have lots of fuel pressure and volume at the schrader valve, but have not put a gauge on it or checked to see if it's holding pressure. I'll get a pressure gauge and find out. The distributor, rotor, and wires are AC Delco and only about 500 miles old. Fresh plugs as well. I haven't tested the fuel pressure regulator with a meter yet, but there is no leaking fuel at the vacuum line. I don't want to change parts just for fun, but the regulator is pretty cheap and easy to change. It's freezing outside and I don't have to drive it right now so I'll order a pressure gauge and better scanner from Amazon today and should be able to give more data in a couple of days. I don't know if this applies to my situation, but a buddy mentioned that some newer vehicles can lose their mapping if left off the battery too long. I disconnect the battery if Im not going to be using it for a few weeks. I've never heard of this before, but thought I'd throw it out there. Thanks again for the suggestions.

Charles

 

[iamdub]

...will there even be any data to read if it only runs 3-4 seconds at a time?

This sounds kinda sounds like VATS (Vehicle Anti-Theft System) is killing it.

...a buddy mentioned that some newer vehicles can lose their mapping if left off the battery too long. I disconnect the battery if Im not going to be using it for a few weeks. I've never heard of this before, but thought I'd throw it out there. Thanks again for the suggestions.

Charles

After the ECM has been reset, it's common for them to stall once, maybe a couple times at most until it relearns idle. You just restart it and let it do its thing. It'll usually rev up, idle low, rev up, etc. until it relearns. This doesn't sound like what yours is doing.


Check this out: https://my.cardone.com/techdocs/pt 77-0011.pdf

 

[crammit442]

I'Ve seen the VATS mentioned. Most of the stuff I saw said that there would be a security warning light on the instrument panel. What you're saying does sound plausible. Edit: I didn't see the link to the document you posted. I'll have to try this tonight. It sounds EXACTLY like my situation. Thank you.
Charles

P.S. I'm going to feel pretty stupid if I crawled around under this thing Saturday dropping the tank and replacing the fuel pump. I'm glad I didn't go low rent and cut a access hole in the floor.

 

[exp500]

Your bluetooth may work. If using Torque app you need to use Torque pro and download GM PID's(other Apps similar)
When you get in truck, turn key to "on" and watch anti theft light. Self tests every time.
Next is turn key on, Wait for pump, off 3 times before you start it. If it starts nicely then usually fuel pump or fuel pump relay.
Also you can check codes key on not running. You do not want a P1345.
Good Luck and report back. These trucks easy.

 

[crammit442]

Your bluetooth may work. If using Torque app you need to use Torque pro and download GM PID's(other Apps similar)
When you get in truck, turn key to "on" and watch anti theft light. Self tests every time.
Next is turn key on, Wait for pump, off 3 times before you start it. If it starts nicely then usually fuel pump or fuel pump relay.
Also you can check codes key on not running. You do not want a P1345.
Good Luck and report back. These trucks easy.

I wasn't able to get my Dad's scanner today, but I should be able to tomorrow. With the key on the anti theft light shows for a few seconds then turns off. When the key is first turned on the fuel pump also cycles. Turning the key on and off several times, the engine starts and runs well for about 3 seconds. Based on the VATS pdf, it looks like my truck is uses Passlock. I followed the VATS relearning procedure several times with no change. I replaced the relay just to be safe, but I don't believe it's bad because the fuel pump won't cycle unless the relay is in place. Reading everything I can find, it sounds like the Passlock module is a pretty common failure. I've watched a few videos on bypassing it, but most seem to be aimed at getting the anti theft light to turn off rather than fully bypassing the system. I see modules on eBay for $50-60, but want to be sure that's actually the problem before buying one. If the system can by tested with a meter I can check it that way. I don't have to drive it right now so I can scan codes before doing anything else. Any suggestions in the meantime? Thanks again for all the help.
Charles

 

[crammit442]

I haven't read the codes yet, but I spent (wasted) the whole evening watching YouTube videos and reading about the Passlock anti theft module/system. Totally down the rabbit hole. It may be something else, but the start and run perfect for 3 seconds symptoms sound exactly like what's going on. None of the bypass videos I've seen actually eliminate the Passlock module/system. Everything I've seen only works to make the computer "see" a key in the cylinder. I found bypasses for installing remote starters, but the Passlock module still has to be good. I don't have a "pill" or smart key, just the hall effect sensor in the key cylinder. There's a YouTube video from an eBay seller (100% positive feedback) that sells a rebuilt module w/a lifetime warranty for $150. There are others, but no warranty. Everything I've seen looks like getting a used one would probably just be buying time. I'm still going to read the codes before I do anything, but the seller looks on the up and up. I'll put links to the YouTube/eBay/website below. Anyone have any experience with this? If I decide to buy one I'm going to buy through eBay w/PayPal/visa for a little better protection. If this does turn out to be the problem I'll make a complete new thread for future reference. Thanks again for all the help so far.
Charles

CHEVY SILVERADO K1500 TAHOE C1500 TRUCK ANTI-THEFT PASSLOCK VATS MODULE 16264955 | eBay

PART NUMBER 16264955. YOU MUST MATCH PART NUMBER 16264955. This is the GM Passlock anti-theft module equipped on 1998-2000 GM Full size trucks and SUV's. Silverado, K1500, C1500, Tahoe, Suburban, and GMC Sierra.

www.ebay.com

93-99 GM Car Passkey Security Module – Pro-Rebuild