NJay1017

my apologies for the late update, it’s on to the next one when it come to this car. so after making three bypass modules & testing them it still wouldn’t start. had it towed to the shop. the only mechanic i trust was on vacation most of the month so it sat about 40days. calls me the day he got into the shop said he cleaned my spark plugs, i had gas in my oil (too much cranking), and minor fuel pressure leak. changed my oil & she started right up. now i can’t remember exactly which bypass i installed but it worked. from there i changed fuel pressure regulator & filter. plugs & wire on the way. also gonna swap out evaporator. change radiator & fans cause she’s running a bit hot now. all that to say she’s back on the road. thank you for all your input.

i’ll post the results when finished (if it works, under a new post just titled “VATS complete bypass”. here is the process so far from all the information i’m compiled. After you build the circuit on your proto board, before plugging in the 555 in its socket and before going any further with the installation, you need to regulate the trimpot R3 to the right value. To do so, point your voltmeter between pin 6 and 7 of the 555 socket and turn the trimpot till vou measure a resistance of 13.5k. Then plug in the 555 in the socket. This way the circuit will be generating a 50Hz signal. Installing the bypass circuit: The wiring diagram of the TDM connector is the following The VATS decoder module has sixteen connector pins, but uses only eight wires An orange wire from B+ for a constant 12VDC to pin B8 A purple/white and a white/black wire from the key contacts A pink/black wire from the ECM/IGN power fuse to pin A1 A dark blue wire connected from pin A2 to the ECM pin B6 A gray wire to the "SECURITY" lamp in the instrument panel from pin A4 A yellow/black wire to the start enable relay operating coil ay pin A3 And a ground on a black/white wire at pin B1 NOTES - Circuit 229 used a dark blue wire in 1988-90, and the circuit passes through the C207 connector between the ECM and dash harness. Earlier VATS systems may have used a white wire for this circuit, but the connection to the ECM on pin B6 and schematic is the same. Some systems may use two white wires between the lock cylinder and VATS decoder module. The key resistance wires may be encased in a black covering, or an orange covering. Some other pins could be also connected, but you don't need to care about them. Now, unplug the connector from the TDM and carefully cut A1, A2, A3 and B1 close to the connector; then strip back the insulation on all 4. Connect the pink wire (that was on A1) to T1 on your circuit; then the dark blue wire (former A3) to your output T3, and finally the other 2 wires (A2 B1) together to T2. Done. Turn on the key and the engine will start right away and never stop anymore. If it doesn't, that could mean that your security system is a PASSKey I and need a 30Hz signal instead of a 50Hz one. All you have to do in this case is to unplug your circuit, unplug the 555 from it, point your voltmeter again on pin 6 and 7 of the 555 socket and this time turn the trimmer till you measure 22.5K.

i thought so but i’ve done every bypass possible. got different results. but a constant no signal to injections.

sorry for the wait. i’m attempting to build 555 to bypass the VATS because i just can’t believe all my injectors went bad at the same time and every other test but the initial (2second of 12v & 43psi) fuel pump is functioning accordingly. when the rest of the kit get here in a couple days i’ll update. if there are any specific electrical test you recommend in the new i’ll knock those out.

that’s my second test when the sun comes up. i just read something in my mania that may have had me & unintentionally is chasing my tail tho. back to the passkey lol. it sends a 50hz signal to the ECM that activates the injectors. that pulse can’t be “bypasses” by simple grounding the wires. and i haven’t made a 555 yet. so passkey back on and “bypassed” w/ resistor like before. battery getting depleted again but i should have enough to check one or two injectors for pulse. if so and pulse. recharge battery and back to jumping prime to get to start or at least find fuel problem.

no shop manual. however while waiting i decided to clean & checks all the grounds & battery terminals cause it definitely sounds like a wiring issue to me as well. both were pretty corroded. swapped them out. both positive & negative cables. that led me to more checks. under the housing where air filter is & vacuum lines lead two were unplugged. from servo? one i think was fuel related. lost daylight so in the morning i’m going to recheck power going everywhere accordingly & attempt to start. then fuel pressure test. then try to ground injectors if necessary. i’ll keep you updated after test. also don’t know if i did or it’s normal to say thank you on these forums cause it’s kind of what they are here for, but i really appreciate all you guys help, input &, suggestions. this has turned into a bit of a passion project for me & as a way too young to be medically retired veteran it’s be giving me something meaningful & productive to do.

okay i’m going to be as clear as possible on this round of results. key on. 0psi gauge. 0volts at prime. 12v at injectors. jumper wire 12v to prime. 12v. 43psi. 12v at injectors. ground injectors. watch gauge. listen for click. nothing. double check to make sure i’m ground them correctly. nothing. no click. no change in fuel pressure.

storm blew in so had to stop where i was. only checked voltages at each one. how would i go about grounding them?

@2seater

there is no voltage to the pump with out a jumper. either c+d or direct to prime.

10.5-12v at all the injectors. however my fuel pressure gauge was still connected as i tested all six. two of the six times (i don’t remember the order) the fuel pressure started fluctuating again. below 30psi back to about 45psi. then would stabilize after about a 30seconds to a minute.

no voltage on the brown next to fuel prime if that’s the wire in question (plug leads to air filter?). stater fluid. crank. pops. no start.

just cranks. spark is good.

0psi and 0 volts to prime when i turn key (everything connected. 12v to all fuses & relay) got steady 43psi w/ prime bypass. got steady 43psi and 12 volts w/ C+D on oil sender.

finally an something i can work with. after installing the passkey harness i made (ground A1, A2,A3,B1 and setting a resistor between A6 & B2) cranks with key like before. no start. spark good. looked a little weak at bank 4 tho. on to oil sender. got 12v at terminal C. moved to fuel prime. no voltage. check pressure no pressure. jumper D+C on oil sender got 12v at fuel prim. 42 psi but erratic. dropping to below 30psi & back above 45psi. the test said it should be steady maybe 1-2psi fluctuation. this is the second series of test that have led me to the fuel system this week. i guess i should start w/ regulator and go from there.