When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I replaced the plugs (Denso), wires (Denso), distributor cap (Made in Japan), rotor (YEC), cleaned out the MAF and throttle body on my 1994 3VZE. Now it won't start. It has very good cranking power, which would seem to indicate that everything is hooked up OK.
I am wondering if unhooking the battery cable during the change-over did something to the fuel that is making it hard to 'catch' and start up? I changed all the above because it was rough idling and threw a code of 25 (or was it 26, can't remember).
Is the VAF (MAF is a different technology) plugged in correctly? If not, the fuel pump will start with key-start, but won't stay running (usually shows up as starts-but-quits-after-a-few-seconds).
Are the plug wires hooked up to the right plugs?
Use your timing light (only $20, and an essential tool) to verify that plugs are firing.
Thanks, Rusty, Scope. I will pick up a timing light after work today and check it out. As for the volume air flow, I never unplugged it when I unhooked the tubing to clean it (should I have?). I figured I unplugged the battery, so that would be good.
Thanks, Rusty, Scope. I will pick up a timing light after work today and check it out. As for the volume air flow, I never unplugged it when I unhooked the tubing to clean it (should I have?). I figured I unplugged the battery, so that would be good.
Not unplugging the VAF to clean the tubing would not be a problem.
Also, disconnecting the battery would not cause a problem.
If you unplug the VAF find out the correct way to do it.
It's very easy to damage it if done incorrectly. You undo the clips not the screws.
Most likely it's something simple that you have done incorrectly or maybe one of the parts is wrong. Check and recheck plug and coil wires.
Marc: Thanks for the reply. Actually, I did try to remove the screws previously to test the air flow to see if it was throwing the code. Then i realized that wasn't the proper way, but, with your instructions, i have just now removed the clips.
If the truck is not running (haven't gotten the timing light yet) is there a way to check the air flow conduit with a ohm meter to see if there is a problem?
If the truck is not running (haven't gotten the timing light yet) is there a way to check the air flow conduit with a ohm meter to see if there is a problem?
Rusty: I checked the terminals using an ohm meter. The only two terminals that didn't measure anything were FC and E1. All the other combinations lit up the meter.
I have a simple Cen-Tech meter that I honestly don't know much about. On the FC and E1 terminals, I switched the selector between the meters 5 ohm selections: 2000k, 200k, 20k, 2000 and 200. No reading on any of those settings from FC and E1. However, since I have the VAF unit all buttoned up, I don't know if the plate is closed or not.
All the other terminal combinations register a reading, typically when set on either 200 or 2000.
However, since I have the VAF unit all buttoned up, I don't know if the plate is closed or not.
The plate will always be closed when the engine is not running. Intake air pulls the plate open once the engine cranks.
Remove the VAF from the filter and you will see a plate inside the air intake. Just push on this plate with your finger and you should show 0 ohms resistance between terminals E1 and FC. (put your meter on the 200 ohm selection)
When you said you cleaned your VAF in your original post, how exactly did you clean it?
Last edited by rustypigeon; 06-05-2015 at 05:41 AM.
To clean the VAF, I pulled the air filter off and disconnected the large air tube that goes to the throttle body. I then just squirted CRC's Mass Air Flow Cleaner Sensor spray onto the plate. When everything seemed dried (I did all this while I was changing the plugs, wires), I re-inserted the filter, connected the air tubing and tried to start the car.
After I posted, and received replies, I then used an ohm meter to check the VAF connection. I didn't actually disassemble the VAF, just squirted the spray onto the plate. It looked fairly clean as it was before cleaning.
I will again pull the air filter out and push the door open with my finger while measuring the two terminals - a bit later this afternoon.
Did anything in that description sound fishy? Or something I might have messed up?
I do not know the 3.0 but the VAF is fairly a rugged built device and doesnt sound like you really did anything wrong on your cleaning. I would say you are ok in that part.
... Actually, I did try to remove the screws previously to test the air flow to see if it was throwing the code.
Re-do your continuity tests. The "usual" way people find out to never remove those screws is by pulling hard enough to break one of the internal traces. Fortunately, it's a pretty simple, robust, device. If it passes the tests in the FSM, you're almost certainly good.
Originally Posted by Rubadub
... The only two terminals that didn't measure anything were FC and E1. All the other combinations lit up the meter. ...
When using an ohmmeter, there is never a situation where terminals "didn't measure anything." It could have measured 0 ohms, or 20,000 ohms, (or over-range), but you can't get "nothing'".
For the FC connection, you only care about "zero" (shorted) and "infinity" (open). So use the 200 ohm scale. Anything less than about 10ohm is "shorted." (The leads have about 0.7 ohms resistance, and there is some resistance where you touch the leads to the connector, so don't worry about anything below 10. Measuring resistances less than 5 ohms requires a different rig.) The Centech meter shows "overrange" (more than 200 ohms in this case) with just "1".
OK, mostly success. Still runs rough, so, it must not have been the plugs or wires or distributor cap/rotor. (Thanks for all the help, guys)
As instructed, I tested the FC & E1 terminals while gently pushing from the inside on the opening valve inside the VAF. It read "1" on my ohm meter before pushing (which I now understand is the starting point for my brand of meter). As I pushed, it went variable.
After confirming that, I hooked up a spark tester to the #2 cylinder and, sure enough, saw the light flashing on the tester. I had spark. After a couple of times of testing spark, in which the truck started and died, on the third time I goosed the accelerator and it caught and ran. I turned the truck off, buttoned up the filter housing, pulled off the test and drove around the block.
As mentioned, it still runs rough. Can I immediately test for the code again by paper-clip-jumping the leads (forgot what they are called), or do I need to drive the truck a way?
I remember several things when I first pulled code 25 or 26: ECT sensor, VAF and something else. How likely is it the ECT sensor waaaaaaay back behind the plenum, up against the firewall?
It read "1" on my ohm meter before pushing (which I now understand is the starting point for my brand of meter). As I pushed, it went variable.
What do you mean by "variable"?
Terminals FC and E1 should show infinite resistance when the plate is closed, and continuity (less than 1 ohm) when the plate is pushed with your finger. Nothing in between.
By variable, I meant that the reading fluctuated as I pushed the plate open. I had the meter on "200" and the meter reading changed as I pushed the plate. It varied. Now, as to whether it was within the range you mentioned, I will go back tomorrow and test, paying more attention to the reading.
If the readings I register when pushing the plate are greater than 1 ohm, what might that mean? And does less than 1 ohm mean that, with the meter set at 200, the reading will be .xx? (hope that makes sense).
The reading should not be variable. Make sure you have your probes on the correct terminals. The FC and E1 terminals are basically an on/off switch. When it is working correctly you either have continuity or you don't, nothing in between.
If you are getting more than about 1 or 2 ohms or so, you have resistance in the switching that shouldn't be there. If there is too much resistance, the Circuit Opening Relay will not close the contacts to power the fuel pump.
-Make sure you are on the FC and E1 terminals
-Make sure you have infinite resistance when VAF plate is closed
-Make sure you have continuity when the VAF plate is pushed open
-Put your meter in the 200 ohm position and report back with the resistance you measured with the plate pushed open.
Here is what the circuit looks like to help you understand what is going on...
Rusty, thank you for your patience. OK, here goes the explanation; I video recorded the testing but have no idea where I could post it and then link from. So, I will try words:
I used the link you posted earlier, http://personal.utulsa.edu/~nathan-b...92volumeai.pdf, to ensure I was hooking to the correct terminals - FC and E1. As I am looking at the pins, those two are to the far left.
With door closed, my Cen-Tech reads "1". As I push open the door, the reading jumps (as high as 9 ohms) but instantly drops to a range that fluctuates (I guess I am not holding the door steady) between 1.1 and 1.3. If I keep my hand steady, it stays at around 1.1.
I tested, with the door closed, the other combinations on the link you provided:
VS-e2: 225 Ohms
VC-e2: 279 Ohms
THA-E2 (guessing at around 100 degrees): 1.36 Ohms
FC-E1: 1 (which I guess is infinity)
As I push open the door, the reading jumps (as high as 9 ohms) but instantly drops to a range that fluctuates (I guess I am not holding the door steady) between 1.1 and 1.3. If I keep my hand steady, it stays at around 1.1.
As long as you don't have to push the door very far to get that 1.1-1.3 reading, you should be ok.
Spark test did fine on all 6 cylinders. I rechecked the error Code, which is 25. I am trying to go, one by one, through each of the Trouble Area listings, which are possibilities, according to the FSM, as to what the problem might be.
I changed the engine coolant temp. sensor and tested (as per above) the volume air flow meter. The other tests are: engine ground bolt loose, open in E1 circuit, open in injector circuit, fuel line pressure (injector blockage, etc), open/short in heated oxygen sensor, heated oxygen sensor, ignition system, ECM.
I pulled the Denso oxygen sensor I installed about 100 miles ago and tested with the ohm meter. It was within the limits. But, I could not test it "heated" because I can't get the truck to run sufficiently to do so.
So, any suggestions on which of that list of possibilities I should tackle first? I used a paper clip to check the FP/B+ terminals on the diagnostic checker to see if my fuel pump was working. I head the whirring sound suggested in the manual, but I couldn't detect anything in the fuel inlet hose (FSM said to listen for a 'noise' from the hose). I just replaced the fuel filter.
06-03-2015, 04:55 AM
