My 92 305 TBI RS starts runs fine most of the time. Once the engine is hot and the outside air is above 75 when I shut the car off it won't start. I was riving the car early spring in 55 degree worked fine. It has spark and will fire on starter fluid but has no fuel. Once the car sits for an hour or so starts back up runs fine but will do the same thing once it's shut off again? Once the car cools off completley the cycle repeats. Any ideas?

Thanks in Advance!

 

1. What is the fuel pressure when the vehicle won't start?

2. Connect a scan tool, find out what the computer is trying to tell you. Look at the data stream, verify EVERY sensor (especially coolant temp, throttle position, and MAP) and computer outputs. "Codes" can be helpful, but the real diagnostic power is in the data stream and bi-directional control.

3. How old are the usual "tune-up" parts--spark plugs, plug wires, distributor cap and rotor, fuel and air filters, PCV inspection, EGR inspection, initial timing, etc.

4. Will the ignition coil fire a spark-tester calibrated for HEI, when the coil is hot and the top of the coil is wet with water from a misting squirt-bottle?

 

I do not have a scan tool, The car runs great when it's cold and hot it just doesn't get fuel once it is shut off hot so I assume the fuel pressure at that point is zero? I hooked up a spark tester in series with one spark plug and the car is getting fire, it starts on starter fluid. Misting squirt bottle?

 

No point trying to work on a computer-controlled vehicle when you can't communicate with the computer. Time to get an appropriate scan tool. Note that "code readers" are not "scan tools", and "scan tools" should also talk to the ABS, air bag, traction control, instrument cluster, transmission--and any other computer-controlled accessories provided the vehicle is equipped with them.

Don't guess about the fuel pressure. You need to KNOW what the pressure is.

Does the fuel pump have a 2-second prime when the key is turned from "Off" to "Run" when cold? How about when hot?

Does that spark tester have an actual gap that the spark has to jump, calibrated for HEI spark output, or is this a useless light-bulb that glows?

Like a Windex bottle--pull the trigger, you get mist instead of a single stream.

 

uncledad, I've seen this, along with GM, when the fuel too easily evaporates/boils. This is why the BBC TBI '94 & '95 trucks run 30 psi fuel pressure. To help alleviate this condition.

It may be the fuel that is in the car. It could be Winter fuel, or just blended wrong.

To help diag it open the hood and let things cool more quickly. See if that helps.

Can also add some fresh fuel to the tank to see if that helps. From a different source.

If what I am thinking is true, the fuel is boiling in the fuel lines up by the engine along with in the TBI unit. Oh yes, GM also used a 'hot fuel module' on certain trucks (prior to the 30 psi units). This ran the fuel pump for 20 seconds at key-on, engine-off. To help cool the TBI unit.

Which brings me to another diagnostic idea. On a hot engine, do a key-on, engine-off. Then after the fuel pump stops (about 2 seconds), key-off. Then key-on again, and repeat for a while to pump cooler fuel through the under hood system. See if that helps.

RBob.

 

Thanks for your reply. Yeah it's something like that, like the old days with vapor lock! My old ford maverick sometimes has an issue starting when hot, I added a one inch spacer and it helped a little. I'm taking the RS to my mechanic to have him test the fuel pump diagnose the issue. I suspect the fuel pump is dying a slow death? I've changed the ICM, no difference. Then I changed the fuel pump relay, I hear the relay click on (not sure I heard that before), but the car still has a long crank to start about 3 seconds or so? I have not tested it since I changed the relay. It also runs sort of hot IMO around 220 or so, I think I'm going to put a 180 deg thermostat and see if that helps, probably won't but maybe? I had a 88 sport coupe in 88 with the same setup 5.0, 5-speed, I don't remember the long crank? Anyway the car runs great when it's cool so once I get the hot start thing figured out hopefully I'll be good to go! Thanks again!

 

Use an OHM meter to measure the resistance of the fuel injectors. Too far off speck could, I believe , cause a no start.

 

Check your coil wire. I had a 350 TBI in a truck that would do this and the problem ended up being the coil wire. It had begun to separate and when conditions were *just* right what was left of the wire would separate and no-start. Eventually it died going down the road which prompted the replacement (spent the remaining time chasing what seemed like a ghost).

You can get a scan tool for these cars, but truth be told for a 1992 it's not going to tell you much. They're still basically dinosaurs even with the OBD-I. Now OBD-II vehicles, that's a whole different situation.

 

Truth. Also verify distributor cap and rotor. The caps will sometimes have burnt center carbon buttons leading to poor spark transfer to the rotor. HOWEVER, since the vehicle starts on starting fluid, this is probably NOT an ignition problem. Much more likely to be a fueling issue--lack of fuel pressure, lack of injector spray.

???

OBD-1 and a scan tool will still allow you to verify EVERY sensor, and most of the computer outputs including fuel trims, IAC steps, and such. They're kinda shy on bi-directional control, and you don't have a misfire indication. Newer stuff has more info...but OBD-1 still has plenty.

The entire thread is kinda humorous--there's a guy like you who doesn't believe that OBD-1 has any info that a scan tool can access--but posts 14 and 15 show what an 1988 K1500 has for scan-tool info. Newer on-board computers can provide even more info even if they're still OBD-1. Keep in mind that this is an ancient scan tool from the early 1990s, based on the FIRST-generation Snap-On "Red Brick" MT2500. As this one is slightly upgraded with graphing capability, it's an MTG2500, kind-of a 1.5 generation model. The software cartridge is good to 1999. Newer tools have more-powerful graphing, more memory, and faster processors.
https://www.automotiveforums.com/vbu....php?t=1146067

 

I was just saying, there’s a handful of sensors providing data for that scan tool on an OBD-I. IMHO it’s not worth it for the $$. I guess for folks who aren’t as mechanically inclined they can be helpful, but the principal of “fuel, air, spark” still applies.

OBD-II systems are taking in a lot more data and have a lot more computer driven items to fail(outside of fuel, air, spark), so I use one on them.

 

Car needed a new fuel pump. Once the engine was hot, outside temp got above 80 or so the pump would not run, wouldn't prime, wouldn't run at all. Replace pump and sending unit seems to be fine!