no codes no spark no fuel

[m1a1battletanker]

i got a 1990 coupe that was running fine then shut off when i parked it for the day. the next day it wouldnt crank. the car has no codes in the ecm or bcm in history or current. all of the 5v refernce signals are there except for the map sensor. there is no spark at all(i even tried it by shocking myself with it...no spark). didnt have a noid light so i used multimeter to check the injector pulses to ground....they fired. all other ecu voltages with key in "on" position are there with voltages crossreferenced from a 730 ecu. checked the ecu voltages twice. the vats is recieving the 2.5v its supposed to and also triggered the vats to rule it out...my key works so its not the pellet. any help would be appreciated

 

[boomdriver]

i got a 1990 coupe that was running fine then shut off when i parked it for the day. the next day it wouldnt crank. the car has no codes in the ecm or bcm in history or current. all of the 5v refernce signals are there except for the map sensor. there is no spark at all(i even tried it by shocking myself with it...no spark). didnt have a noid light so i used multimeter to check the injector pulses to ground....they fired. all other ecu voltages with key in "on" position are there with voltages crossreferenced from a 730 ecu. checked the ecu voltages twice. the vats is recieving the 2.5v its supposed to and also triggered the vats to rule it out...my key works so its not the pellet. any help would be appreciated

Please define "would'nt crank"....
Do you mean to say that it cranks ( turns over) but does not fire? if so, look at the ign module, its wires inside and up to the distributer.Some auto parts stores can test the GM ign modules. Ck fuel pressure. There must be at least 25 lbs to build a fire. Norm is about 40.

if it won't crank (turn over) then most of those numbers that you have are false...if it DOES "crank" but is not firing, thats one thing.

If it does not crank at all, then VATS cannot be ruled out since the VATS has different means of disabling the engine.

Vats only reads a resistance, not a voltage.

 

[m1a1battletanker]

sorry......... wouldnt crank= turns over but no fire. im going out right now to check the injector resistances and also check the pickup coil and associated wiring. what i was referring to as far as vats voltage....the ecm recieves a 2.5v signal from the bcm for the th ecu to assume the car isnt being stolen. all of the vats runs through the bcm if im not mistaken

 

[Hib Halverson]

1) Do you have the factory service manual?

2) Have you consulted the diagnostic procedures listed in the FSM in Section 6E under "cranks but won't run."?

 

[m1a1battletanker]

all of the injectors check out at 15-15.3 ohms. i have power at the pickup coil. all of the plastic surrounding the wires leading to the pickup was broken off either from vibration or previous owner. i know somebody has been in there though. i decided to pull the codes again and this time i got 3 codes all in the bcm history. code 41 for module 1-loss of serial data from ecm and then 72 and 74. now how do i alleviate the loss of serial data and is that whats keeping the car from running. just some history on the car since ive had it(1.5 months) ran beautiful for a while. it started acting like it was fuel starved and would choke itself on a quick throttle. one day about a week before it finally quit i was sitting at a red light and it idled fine but when i went to roll off it spit and sputtered til i pulled over then revved it a few times then it was fine. the car started getting harder to start even if it had just been running within 5 minutes it was hard to start and then finally no start.

 

[m1a1battletanker]

no i dont have an fsm. the only resources i got are this site and experience from other vehicles. this is my first vette. where is the bcm located so i can check for loose wires there since i got the code sayin loss of serial data

 

[boomdriver]

no i dont have an fsm. the only resources i got are this site and experience from other vehicles. this is my first vette. where is the bcm located so i can check for loose wires there since i got the code sayin loss of serial data

Pull a plug to see if there is any fuel....it should be obvious if there is fuel being inj and no fire.
Just because they are getting pulses does not mean they are getting fuel. Back to fuel pressure/filter/relay/pump.

ECM is located vertically in the passenger side dash. Remove floor panel, look up to see two 10mm bolts. Carefully remove the 2 ECM plugs, remove the 2 bolts and it drops straight down.

Everything on a C4 or newer Vette works in loops with the ECM & BCM (if your model has a BCM...don;t think 90 did). One thing gets its signal or OK to function by looking at signals from other things...like fuel for example...the fuel pump gets ok'd by way of a relay that gets the signal from dist pulses.
No dist pulse (sign of rotation)...no fuel..But even that has back up. Oil pressure also signals rotation and closes a switch that can send power to the fuel pump. Point is, that the systems depend on each other and will not operate without the ECM enabling and this makes it susceptable to the domino effect.

If you found damaged wire going to the distributer, I'd be looking at the module. Coils rarely die, but modules can short out easily with the wires contacting ground or each other.
Since everything operates on ground path completion/control from the ECM, having a control ground get a charge of voltage can do some damage.This ign generates 40,000V discharge from 12v ...That is extremely time sensitive, so the module must be working in order to have sufficient discharge voltage to fire a plug. Shorting out right there is an interruption of critical data to the ECM.

Locate the G-104 bundle of grounds (4 or 5 wires, one bolt) on the block or bellhousing near the oil filter, check the fusable links for loose wires or corrosion at the bundle/jumping post behind the battery, and test fuel pressure. It'll take a gauge. Gas will spew from the schrader valve with 2 lbs behind it...you're looking for 40.

If pressure is low, a filter or clogged sock is to blame. Intermittent run and throttle issues come from the filter being near plugged. After sitting and pressure bleeds off, sediment settles and gas can flow normally again. Then out of nowhere it starts burping and coughing under power again.The filter has plugged again and pressure has been cut off.

 

[m1a1battletanker]

this is where it gets fun for me. im very disabled and dont have the money to play with buying more stuff. nobody wants the car cuz it dont run and the last of my funding for the month is in the gas tank. i guess im gonna pull the pickup coil again and take it to get tested. earlier just for kicks i went out and messed with the wires in the dash and tried to start it again and it hit once but that was all

 

[djsroknrol]

Does the distributor check out?; i.e., is the distributor doing its thing?.....I've had a bad cap and a sheared drive pin in the past that drove me nuts for days.

I've since learned to look at the obvious first

 

[boomdriver]

this is where it gets fun for me. im very disabled and dont have the money to play with buying more stuff. nobody wants the car cuz it dont run and the last of my funding for the month is in the gas tank. i guess im gonna pull the pickup coil again and take it to get tested. earlier just for kicks i went out and messed with the wires in the dash and tried to start it again and it hit once but that was all

Dude...
I hear exactly what you're saying...all of it.
Thats how I know what I know...had to learn the same way or get a bus pass...
I'm not in prime shape either, so I'll help you thru the easiest things.

One thing at a time...

do the module first. If that test OK, we go from there tomorrow. In the meantime try to repair as much of that damaged wiring as possible, even if its only black tape. It'll be better than it was.

Hang in,,,we'll get it going thru ->state of the art long distance diagnostics..<=-

it'll be there tomorrow, and so will we !

 

[m1a1battletanker]

bus pass would be nice but i live in the sticks literally 20 miles from anything lol. the wires from the pickup coil look good except for the inch or so thats inside the distributor where the purple/white wire was the same oily yellow as the other wires inside the distributor. the cap and rotor button are new. the coil itself is good. i did another spur of the moment thing a while ago and pulled the ecu from under the hood and took it apart. the whole bottom of the circuit board where it is the lighter green foil looking was all crinkled up everywhere and looked like wet toilet paper that dried. i kinda suspected the ecu got wet somehow but all the seals were good and it took me a good half hr just to bust the seals on the case loose. the prom chip on the ecu was a little loose and the tabs on it werent locked down. i will reinstall the ecu tomorrow and hopefully find a jump start. this is really messin with me hard but only because this car is my only means of transportation.

 

[m1a1battletanker]

oops just realized that i was mistaking the ignition control module for the pickup coil guess ill tear it back apart tomorrow

 

[boomdriver]

oops just realized that i was mistaking the ignition control module for the pickup coil guess ill tear it back apart tomorrow

That little ign module is a little flat plastic box about 3" wide and has metal contacts on each end. Important that it sits on a good layer of silicone grease or ign grease for heat transfer.

I forgot that your yr moved the ecm under the hood...easier to get to for sure. I think in 91 they started using a bcm for body/chassis functions along with the ecm strictly for engine mngt.

 

[m1a1battletanker]

well i finally got the car to throw a code today but it was just a code 72 for current and history which by my account says led dimmer circuit malfunction. that cant possibly keep it from starting can it?

 

[m1a1battletanker]

just want to clarify that im pulling codes with a-g on the aldl and the code 72 is module 1(bcm). i get no codes for the ecm with a-g on module 4 or with a-b jumped

 

[boomdriver]

well i finally got the car to throw a code today but it was just a code 72 for current and history which by my account says led dimmer circuit malfunction. that cant possibly keep it from starting can it?

Not as far as I know, but it does offer a clue..

power or ground interruption?

I know that the wire harness section behind the left bank on the firewall has ALL the splices that take off for the injectors, the temp sensors, oil press, low press switch, all intake sensors and switches and those important grounds.
It tends to rot within the insulation and cause all form of grief.

Just for fun, see what that looks like and what kind of shape the bundle is in. The splices suck....with black tape from the factory under the plastic sheath. Try to wiggle that around (can't get to it easily) and see if that does anything. Your power to the dist comes from there and that IS the path to the ecm.

 

[m1a1battletanker]

well the dizzy has power in all forms just not sparking. that harness you speak of i looked at earlier today and frankly thought to myself the whole thing needs replaced. the whole outer sheathing on it is dryrotted and crumbling apart. how far down that harness are all the ground splices? is there an easy way to get in there? lol where exactly are all these fusible links i keep hearing about and wut do they look like? i wiggled that harness around and have a battery charger on the car to try a voltage boost kinda thing lol i know stupid but i have a knack for doin dumb stuff to get things to work. ive kicked lawnmowers and punched computers and they worked thats how im typing this lol. guess ill kick it tomorrow

 

[m1a1battletanker]

lots of weird of stuff happening now. i decided to really pry into the ecm harness looking for the obvious electrical faults. now all of a sudden since i messed with it vats has kicked in full force and will not reset and all of a sudden my horn works when it hasnt worked since i got the car about 2 months ago. the wipers flicked up and down 1 time and also all of a sudden the chimes work in the car. i hate electronics

 

[John Robinson]

Now you have somewhere to start. Get some electrical contact cleaner and remove the ECM and the four electrical plugs.
Clean the post and pins for the electrical connections with the contact cleaner and put it back together. Don't forget that a lot of stuff because it uses low voltage will work even if the battery has a bad cell. Just for grins hook a voltage meter to the two battery post and try to start the engine. The meter should not drop past 10 volts if it does then you have one of two things happening a battery that will not hold a high enough charge to turn the engine and supply the voltage needed to run the ecm so it knows what is expected from it. It probably goes without saying but I am going to anyway. If the battery test good but has a low charge then the alternator is the next culprit. I have had battery's get a direct short between cells and the car just shuts down.

 

[m1a1battletanker]

well the alternator is new so that narrows it down a bit but doesnt explain why all of a sudden my horn works. well i finally got the vats to let go now i am kinda back at square 1 with no spark no fuel no codes but it will turn over. clutch safety switch is bypassed with the wires twisted together with a wire nut and electrical tape(not my work, i just go by if it aint broke dont fix it.) im going to go ahead and make some room to work with tomorrow