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454 Fuel Problem |
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Romeo 
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Joined: 16 November 2008 Location: Canada Status: Offline Points: 3033 |
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 Topic: 454 Fuel ProblemPosted: 24 August 2011 at 3:47pm |
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Alright, I figured since you guys nailed the first problem I had with the 454, I'd head to you for my new issue. Notably, the distinct lack of fuel from the injectors. Now, to rule out the things I know it isn't: Fuel pump, injectors, connectors to the injectors. I have verified that there is fuel flow to each injector, and that shorting the injectors causes them to shoot fuel out as normal. The connectors leading to them are all at 0.1 Ohms resistance, which is well within a usable range. So it's something electrical leading up to the injectors. I've checked the wiring for about the two feet leading up to them, but after that, it goes in to the wire loom that heads to the PCM. Basically, long story short, I don't want to grab a whole other computer from Pick-A-Part only to find that isn't the issue at all. Given that the 454 uses almost the exact same system as the Duke does, any ideas on why the PCM isn't signalling the injectors to fire? I'd really appreciate any advice on the matter, thanks! |
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Dr.Fiero
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Joined: 12 February 2007 Location: Canada Status: Offline Points: 1726 |
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Posted: 24 August 2011 at 4:57pm |
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So - since you didn't mention what year n' stuff other than it's a BBC... I'm going to pretend it's a '93 K3500.
You have constant power (key on) at the red and white wires, right? Hook up a test light, or a scope (yeah right) to the red, and to the dark blue OR the dark green and crank it. Light should blink. Wanna get fancy, hook up two lights, and they should alternately blink. Will it run on ether/trickled gas? |
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Romeo
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Posted: 24 August 2011 at 5:19pm |
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Haven't tried dripping gas in to the intake, will do that next. What do you mean by red and white wires though? My power wires are blue and brown, respectively. They're powered.
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Dr.Fiero
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Posted: 24 August 2011 at 8:10pm |
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Well like I said - I just picked '93 K3500 randomly (and looked up schematics accordingly). What do YOU have?!
 But anyhow, if you know which pair are powered, just run with the concept. You're just testing to see if the ECM is grounding them at the right time. Don't guess though. Test 'em. |
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Romeo
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Posted: 24 August 2011 at 10:56pm |
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K2500, I'm sure it's the same (motor-wise). Anyways, I don't have a voltage meter capable of checking the brief "on-time" of the circuit, but that would be irrelevent... When I forced 12V through the wiring leading up to the connector, injectors fire just fine. |
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Dr.Fiero
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Posted: 25 August 2011 at 5:47am |
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That's great - but I didn't say to use a meter. Test light.
Also didnt say to try and force them to fire! You're looking for ground pulses from the ECM. Hope you pay more attention in class grasshopper!  |
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Romeo
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Posted: 25 August 2011 at 12:01pm |
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Don't have a test light, so that'll be an issue. As for looking for the ECM to ground them out, I know that it isn't. Mechanically, the fuel system is good, and electrically, it's sound. So I know it's the ECM not doing them, I'm just trying to figure out why.
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Romeo
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Posted: 25 August 2011 at 2:51pm |
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AlRIGHT. Having taken the truck from it's original lack of fuel delivery (No fuel) to massive over-fueling (Too much fuel) to lean misfiring (Not enough fuel) I've finally got the issue figured down to one part, more or less. Because I realized the fuse got wiped when I shorted the injectors through the battery, I had an added issue to contend with there. Replace the fuse for the injectors and now the driver's side injector works, while the passenger's does not. Here, however, is where common sense simply goes out the god damn window. Because both injectors are treated effectively as an alternating pair, I can now rule out other sensors from the equation (Distributor signal, O2, Oil Pressure Sensor) as those faults would cause both to not work. Looking at the power delivery, I know that the driver's side was working, so to check if it was either power or ground, I decided to "bridge" the two power sides at one point, and then the grounds after that. Now, before you go hollering "But Tristan, you sex god, two injectors takes twice the power!" know that at idle, the injectors are "off" more than they're on, and they alternate back and forth. As far as the system is concerned, it isn't running two injectors at the same pace, it's running one injector "more often". Bridge the power sides, and the driver's injector simply cuts out, just like the passenger's side (Removing that bridge causes it to work again). Alright, I thought, a little odd, but I will continue to ground. Now, this is where things would be "different" for the electrical system. In this circumstance, we're assuming power is being supplied to each injector, who are then sharing the ground signal. This does affect amperage and signal, so it's not a direct comparison to "working right". However, once again, bridging the grounds simply wipes out the driver's side injector as well (Without blowing the fuse, or destroying the computer, as the injector will work as soon as the ground is removed). So, basically I'm at a point now where I have as many variables taken out of the equation as I can, but the remaining solutions no longer make sense... Any more help Doc, or anyone? |
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Dr.Fiero
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Posted: 25 August 2011 at 5:39pm |
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Have you tried simply flipping the connectors around (left for right) and seeing if the problem follows the connector, or the injector? TBI injectors clog and/or die fairly easily. They (TBI units) are also prone to regulator failure. It's built into the 'head' of the unit. Done a number of them.
As for no test light... you mean to tell me you don't have a couple of spare fiero corner markers/dash light bulbs? The wires unfold nicely. Poof. Test light(s). As for bridging the power leads - nothing should happen. They both go back to the same point on the fuse panel anyhow. Bridging the ecm's side... well.... not a great idea, but it shouldn't burn out the quad driver if you don't do it for long. Not a good plan though. |
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Romeo
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Posted: 25 August 2011 at 7:20pm |
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Up until two minutes ago I'd have said your suggestion of swapping the connectors would've been pointless. After all, I knew when I shorted them, both injectors would fire no problem. Switched the connectors and realized I owe you a sincere apology. For whatever reason, even after switching the connectors, the driver's side is still the only one firing, so I'll have to pull the passenger's side and replace it. Thanks Doc! As for bridging the power side, I know they both come from the same fuse, but I was wondering if perhaps one side's power supply wasn't making sufficient amperage to open the solenoid (Injector) up, so I was wondering if bridging it would highlight any power-side issues for the one injector. And agreed, bridging the ECM was a dicey move to be sure, but like you said, it's survivable if done for a short enough time frame. Lastly, no, no spares or extra bulbs/marker lights of any kind. |
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Patrick
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Joined: 19 April 2008 Location: Vancouver Status: Offline Points: 5 |
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Posted: 26 August 2011 at 9:21am |
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Sorry bud, you lost me after the "sex god" reference.
Tristan, please read (and respond to) your emails!
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Romeo
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Posted: 26 August 2011 at 6:14pm |
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OY, DON'T TELL ME WHAT TO DO, OLD MAN. lol |
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Romeo
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Posted: 18 September 2011 at 2:40pm |
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Well, after several screw-ups and delays with Lordco, I finally ended up going to Burnaby Auto for my injectors, and today I got the truck running. Only problem being, it's barely idling, and throwing black out the tail pipes (Indicating MASS over-fueling). My only question is this: Is this an issue I should try and correct somehow? Or is it just the result of the fuel map having been enriched when the fuel system was failing, and I should just let it work itself out? Any help would be appreciated, thanks!
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Dr.Fiero
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Posted: 18 September 2011 at 2:55pm |
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No way short or long term trims are going to fix THAT much
overfueling (black smoke). You might have a broken or rusted out spring in the FPR (common problem btw). |
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Romeo
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Posted: 18 September 2011 at 3:23pm |
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The regulator is only supposed to come in to play during WOT (In terms of fuel mixture), is it not? A high regulator pressure will only mean the ECU has to pull back more fuel, doesn't it?
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Dr.Fiero
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Posted: 18 September 2011 at 3:56pm |
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It is not.
It modulates the pressure at all times to maintain a constant pressure at the injector. It would make writing the fuel tables insanely difficult if the pressure kept changing. The ECU can only vary the mixture by a small amount (can't remember the percentage) from it's base #. |
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Romeo
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Posted: 18 September 2011 at 3:56pm |
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Well Doc, it ain't the regulator. I threw on the 305's regulator in to the thing, and there was absolutely zero change (Not to mention the 454's regulator moves freely). I will try popping off the return line though, and just running a fitting in to a bucket. Maybe the return has some sort of blockage.
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Romeo
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Posted: 18 September 2011 at 4:53pm |
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Well, I'm at my wits end. I had almost thought perhaps a couple of plugs weren't firing (Hence the rich exhaust, and lopey idle). However, when hit with some gas, the exhaust clears up, and it revs insanely quick... UGH. Last GM truck I buy, I swear to god...
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Romeo
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Posted: 18 September 2011 at 5:20pm |
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Sorry for the back-to-back-to-back post, but I took it out for a few laps around the block, and I've discovered a few things:
Help? |
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Dr.Fiero
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Posted: 18 September 2011 at 6:38pm |
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Not placing any bets or guarantee's, but....
From what you've just described, it sounds like your MAP sensor is not hooked up, not hooked up right, not working, not wired, not... well, you get the idea. Wow - I'm really surprised someone hasn't jumped in here yet with a solution via a semi relevant link to a long dead thread on Pennocks. |
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Romeo wrote: