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tbi troubles..it wont fire

T

Txchevy18

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Ok guys I need some help. Im
in the middle of a total rebuild.. 1tons, xover, hydro assist 700r4/np205 freshen up tbi 350..ect. on a 88 k5.

I can get the darn thing to run. The wiring has been previously molested so ive had some fun figuring a few things out.

OK as of now it will turn over without a problem.
I have spark, at #'s 1 and 2 for sure(dman that coil hurts...). it has new plugs and wires.
I never messesd with the dizzy at all.
I have fuel from the injectors when cranking, but only when the accelorator pedal is pressed. no fuel that i can tell at idle.
Ether wont start it... Nor pure gas straight into the tb.
Timing is good now.
The fuel pump relay is brand new and when the battery is removed and re attached it clicks so i would assumse its work properly.
Pulled dizzy and reset it.
I checked firing order 3 or 4 tiimes that not it..
It just wont fire!
Btw the trannsmission and t-case are not in the truck at this point.

Tommrow im goin to buy an inline spark tester. Other than that im out of ideas...


Im at wits end with this dang thing. Im sure it something im over looking but I just dont see it any ideas would help out immensly!

thnx
Cory

If yall need any more info or pictures let me know.
 
If you can't get it to fire with ether, either you've got spark or *bad* timing issues.

Someone can surely comment on what TBI is supposed to do with the pedal floored, cranking. I'm thinking NO gas, but not certain.

Procedure is the same for 1 or 8 plugs to fire, if one will fire, they all should. No way other than a bad cap or wires that the dead cylinders would be consistent.

Power the fuel pump via the red lead, does it run? If so, leave it hooked up like that and see if it will run. You get the 2 second prime when the key is turned from off to run?
 
Ok I messed with it some more today heres the results.

I swaped wires to check to see if I was 180* out , No luck.
I also picked up a induction spark tester tool and verified spark at all wires.
I removed wires to verify correct firing order once again.
By reasonable elimination I thought well hey maybe the coil isnt producing enough spark.. new coil still no go, not even a sputter.
I reset timming again according to my hanyes manual no go.


I did start thinking and may have a possible solution/problem though. When I bought the new spark plugs I got them a level colder since I am planning on installing my jacobs prostreet ign and coil. The previous owner was that i bough it from was fouling plugs left and right on his tahoe. A co worker said the colder plugs should fix my problem. Is it posssible the spark isnt hot enough to lite the fuel? I plan on picking up a new set of standard ac delco's to try in the AM.

Other than that im lost... Any ideas guys?

As for the fuel pump the previous guy just replaced it.. ( he was lazy and cut a hole in floor.. GRR) I must say though its the quitest fuel pump ive ever heard and would swear it was the problem if i didnt have fuel pressure. I also noticed that the injectors are actually firirng at idle..
 
Colder plugs aren't going to affect a properly working setup like this.

You say you have fuel pressure...I'm missing that in your previous posts apparently? This has been checked with a gauge?

No fuel out of the injectors while cranking is a problem. You verified this with an assistant? Something is either telling the ECM not to open the injectors (bad coolant temp sender?) or something is going on with the fuel pump/pressure.

It's as simple as this: if you don't have fuel squirting out of the injectors while cranking, with spark, cold engine, no throttle, there is a problem with the fuel delivery or ignition system.

Got a scanner handy? Real quick test for the coolant temp.
 
Ok I will verify the fuel system tommrow . I have a friend who belives his scanner at work will work on my truck so were gonna try that. Yesterday I had noticed that the injectors werent firing at idle(no throttle) wny turning over the engine. Today my buddy made a comment that they were infact firing at idle while cranking. The only thing diffrent was I had noticed a orange plug that was oval with the lower corner cut in wasnt connected to it sensor in the back of the block. I pluged it in before messing with anything 1st thing this morning.

I did a some reading and studying of the wiring diagrams i have in both my chiltons and haynes manuals. I noticed a plug with two wires not conected to anything on the passenger side of the block on the intake side of the valve cover. IF I remember correctly it went to the evsr(electronic vaccum sensor.... or something like that. Could this be a problem? I also dont have a trannsimission or , or t-case under teh truck but dont belive that would be a problem. Thanks for the ideas thus far. I apperciate it.

Cory
 
So if you DO have fuel while it's cranking, your ignition system is "fine". (you don't get fuel if the ECM doesn't see spark)

I don't know anything about an EVS on these systems, could be something to control EGR, AIR, or the like, although most of that stuff was all electronic I thought. EFE maybe?

Double check hoses and what not, make sure you don't have a big vacuum leak for some reason.

You've brought it up to TDC and verified timing is dead on?

Transmission not being there shouldn't matter.
 
Well that rules out the igntion system as my problem then...
I guess ill go look for a vaccum leaks. Would a vaccum leak actually cause it to act dead?
Also whats and EFE?

As far as timing. I brought the timing marks together and lined them up. Then removed the dizzy and reinstalled it with the rotor facing towards #1.
Ive turned the dizzy both directions with no luck. I havent got teh thing to sputter yet it just doesnt make sense. IF it was 180* then it would blow back up through the tb right?

Thanx and ill keep trying
Cory
 
I found this guide on affordale-fuel injections website. Would the intion system function as it does with a bad module in the dizzy? It seems highly unlikey in my opion but these guys do this for a living ..

Remove plug wire and check for spark while cranking.
No Spark – Repair ignition system.
Has spark – Insure wire continuity between the ECM and the distributor or tach
Filter. If fuel is still not spraying go to fuel system troubleshooting before replacing any components. If all wires are in tact and routed correctly and all fuel system checks are correct, replace distributor​
module or tach filter.

 
A scanner that works with OBD1 is supposed to show RPM's while cranking. This data is sent via the ECM, so if there is RPM shown, the ECM is getting the signal they are talking about with the continuity test.

Personally, on my setup (not TBI) I've never been able to get that test to work with the scanner. Even the GM manual says you are supposed to see the cranking RPM's, but since mine starts, the problem is with the scanner. Different scanners may work correctly.

The module controls spark, if you've got spark, I don't see how it could be the module. Tach filter, well, TBI trucks didn't come with tachs. (at least not the '87-91 R/V's.
 
I saw an obd1 otc scanner at autozone this morning when i was dropping off an old core for a friend. I belive it was in the 150$ range, I may pick it just to have and trouble shoot with. Besides you never can have to many tools. But i dont belive ill pick anything up since the engine wont start the ecm doesnt have any type of data to log to determine that theres a problem. Am I on the right track or way off in left field?

I did a some more research and found the metion of a wire thta had to be disconected to set base timing at 0* then reconnect and allow the ecm to take over from there. the wire seemed to be commonly tan or tan and black located on the passenger side firewall.

Ya ive done a lot of reading on your tpi swap. I actually have acess to a entire motor and setup but opted for this since its a dd and for the time being simplicity is bliss.. or so i thought.

Thanx
Cory
 
Yep, once you understand the TBI system, you'll realize TPI is no more complex. People think it is, but that's because there are 8 injectors. Big deal. (other small differences, but not that big)

The scanner will actually tell you a fair number of things. It's not the end all tool, a lot you can do with a multimeter, multimeter is more labor intensive. Scanners and multimeters aren't the end all diagnostics, if there are intermittent issues, or things that happen too fast for the scanner/multimeter/human eye to notice, there are more tools out there, but cost becomes an issue. A multimeter is *required* to be working on this stuff though.

For instance, with a scanner, you can tell in 2 seconds if your coolant temp sensor for the ECM is good or bad, and also if you wanted, verify your gauge with the ECM temp reading. Your TPS is also a 2 second check for voltage and sweep. Engine RPM is another.

Key only needs to be in "run" for the scanner to work, as the ECM is powered and monitoring all sensors at that point. Engine doesn't have to be running for certain measurements, like the ones mentioned above.

Alternatively, if you've got a laptop, you can download winALDL or tunerpro RT, build the 160 baud cable, (easy) and use the laptop as your scanner. It's a lot cheaper, and actually more utilitarian than a scanner. Bit more of a hassle to set up, bit bulkier, but less than $10 if you've already got a laptop with serial port.
 
Ya im starting to realize that. I may be preping things for a tpi swap soon if i can get my other truck titled.

I Plan on borrowing my buddies scanner tonite so that may tell me a more about whats goin on. I actually do have a laptop I could use for this. I just replaced my grandparents old one so it just sits on a shelf. i have seen the aldd cables for sell and seen several metion building there own but never found any info on the diy side of it. I have several large electronics stores within about 20 miles so gathering the pieces should be a problem just need a how to.

I picked up a set of ac delco plugs to try. That should aliveate the one thing i did change from the last time it was running. So we'll see.

Thanx again,
Cory
 
http://winaldl.joby.se/aldlcable.htm

I built the one in the first diagram. But ignore the pinout picture, (the connector) when you look at a real serial cable, you'll see the diagram is numbered wrong. The wires need to go to the same pins as in the diagram, but the picture in the diagram has the pins labeled incorrectly. (reversed IIRC)

Radio Shack has the components.
 
Did you get that two wire plug installed? You certain that's not the ECM's coolant temp sensor?
 
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