302 EFI in an '87 E150 van. It rained hard earlier today, first time in many months. It was not an especially hot day.

Was running dandy on the highway a few minutes from home. Suddenly, nothing, one backfire pop. Tinkered with it awhile, had it towed home.

Starter cranks it over fine. No hint of ignition no matter what you do with the pedal. Have fuel pressure, 40 psi at the injector manifold, upon turn of key. It's not foamy air, just fuel. Air cleaner is off entirely so the intake's not blocked. Have spark at the distributor head. Distributor rotor is intact. Fuel injector wires show pulses on a scopemeter.

In my experience, the codes on this pre-OBDII are useless and hard to read anyways.

Sprayed some B12 Chemtool into the dual intake hoses. Maybe it wasn't enough, but the engine didn't respond.

It was running fine right before it died, so I'm ruling out anything that would screw it up on a cylinder-by-cylinder basis. Not a clogged injector, for example.

I'd normally say "it's the TFI, that's what causes Sudden Engine Death 90% of the time". But there IS a strong spark at the dist center, and AFAIK all TFI failures are no-spark conditions. Sometimes they fail intermittently, but I have spark right now but no "go". Also rules out ignition coil.

I have fuel and fuel pressure. It's not the Fuel Cutoff Switch- mine melted years ago and the two wires are nutted together. Anyhow, there's pressure. The pump works.

Vacuum hoses look OK.

I have wondered about the catalytic converter, it was noisy awhile back. Totally clogging up suddenly seems unlikely, and the engine doesn't sound any different than normal turning over. I'd expect it to start initially but bog or die due to excessive backpressure, or at least sound "hollow" if the exhaust were clogged.

I did not smell fuel at the exhaust. This is confusing, with injectors pulsing and no ignition I'd expect there to be some fuel in the exhaust.

I had the timing chain jump once, ~5 years back. Back then, I recall it cranked just like this, no hint of ignition and there was no fuel smell at the exhaust then either. But it hasn't had that many miles on it since the timing chain+sprockets replacement, and the engine didn't funk out from a starting attempt which is when it "jumped" last time. If it's loose I'd expect it to jump on a starting attempt. Sure, I suppose if it got loose enough it could indeed jump on the highway at fixed speed, but it probably won't get there because it's gonna jump on a start before that and never get stretched bad enough to jump during constant-speed driving.

And there's fuel pulses, which mostly rules out the ECU. Well, not entirely, they could be too lean. Could stick the EGR valve open and there's two other vacuum valves, but AFAIK those aren't critical enough to cause a no-start.

Any ideas? I'm kinda outta ideas.

 

Added a crapload of B12 Chemtool to the intake hoses (like half a teaspoon each) and gave it an extra-long cranking. It didn't help- still no hint of ignition!

 

Rocked the crank back and forth to check for timing chain slack against the distributor rotor. There's nothing significant. Thus the timing chain could not have jumped.

The dist cap's center button is intact and springy. Cleaned the dist rotor earlier. The rotor's spring is fine. The timing test plug is in place. I rechecked the spark for kicks- there's plenty of spark at the dist center.
Went ahead and checked spark at a cylinder. It's there, and strong.

The tank switch hasn't worked in years, and the gas in the front tank is years old. I always use the rear. Had a theory that stale gas from the dead tank was suddenly getting pumped to the engine. It doesn't smell sour though. I got it to spray out of the schrader valve onto some paper, hit it with a lighter, and it went "poof"... FWIW.

This is just rapidly going nowhere. Fuel, compression, spark= run. Have fuel in rail at 40 PSI, have injector pulses. Have spark at cylinders. Valves can't have screwed up on both sides of the engine at once, and the timing chain isn't loose. The camshaft's not gonna just BREAK and make a no-compression situation.

And if it was gonna foul, well, it did rain but there was a gas cap on it of course. Has been running on this tank for a week and didn't bog down gradually... just "poof" and the engine stopped. I added 3 gal of fresh gas from the corner station first thing, on the theory that maybe I DID just run out of gas.

 

Have you lined the timing marks up and looked where the rotor is pointing? My timing chain wasn't loose either,and my truck did the same thing,backfire,then die and no start,fuel pressure,spark,everything was good. Loosen the distributor,turn it and try to start the engine. My truck started like this,but when I checked the timing with a light,the marks were WAY off.

 

yeah, this sounds exactly like a timing chain. those plastic gears will wear just enough for it to jump time, and every once in a while they will start and run still, but horribly. I would hook up a timing light and check it just to be sure.

 

Doesn't have plastic timing chain gears. I changed the timing chain personally like 5 years ago, of course it's a metal timing chain set. Oddly enough I'd paid someone to change the timing chain like 30K miles before that, on general principle, because the vehicle was >10yrs old. The timing chain should not have worn out so early after that first replacement, but it was failed, the sprocket was visibly worn.

I had theory that the repair shop had not performed the first replacement at all, just blew me off and took my $. However, the timing chain set I took out after it failed 30K miles after that was NOT the dreaded factory nylon-tooth one. I had a theory that the previous owner replaced it at some point, I missed that looking through his records, my shop scammed me on the replacement, thus that timing set had been running like 100K not 30K.

I'd be willing to believe there's some kind of Timing Chain Eater at work here, but I've never heard of such a thing. An abrasive condition in the oil will destroy the engine long before the chain. And the fact is the chain's not broken nor showing slack.

But I'll certainly check the timing... it's not like I've got any better theories at this time.

 

never heard of a chain eater either. (sounds kinda scary though!)

hmm... this is a chin scratcher then. let us know what you find with the timing. maybe we can think of another reason.

when i first fired up my falcon (after 20 years sitting in a pasture) it would start but would run longer than 5 seconds or so, then back fire throught the carb. that turned out to be the exhaust plugged with mouse nest. strangely enough that little 144 is one of the best running little engine i have owned.

got fuel, got spark, got air. your gonna check the timing, I have seen cam break, but usually in new engines that the builder didn't check the clearances in, so i doubt it as well unless of some fluke chance.

maybe the chemtool wasn't enough? could squirt some gas down its throat, but the b12 should have done it.

you could go ahead and try pulling codes, yeah they don't compare to obdII, but they can still help guide some, if there is any there.

bummer bout your shop ripping you off though, they give the good guys a bad rep.

 

Physically unscrewed the O2 sensor, so even if the exhaust were completely plugged it would be able to exhaust through that hole.

No luck. Looking for the timing light now...

 

I had the same problem with my `90 f-150.. The culprut was the distibutor pip sensor.Try swapping the distributor with another one that you know is good to test it out.

 

Well everywhere I read, if the PIP sensor's bad, you won't get injector pulses at all. I have injector pulses and spark.

I tried to get a timing light in there, but without the engine running, it's just too slow on the starter for me to make out anything and I'm gonna burn out the starter playing with this.

I used a breaker bar on the harmonic balancer to crank the TDC mark to the line and checked the dizzy. Hmmm... the rotor does SEEM to be off from pointing at the #1, maybe 1/3rd-1/4 of the way to the next stud. Hard to say for sure, and timing chain is not a simple try-it-and-see-if-it-fixes-it thing.

Wait... if the timing chain slipped, then the crank should be ahead of the valves/distributor position. The rotor turns counterclockwise, and it's past the stud in a counterclockwise position. Well jumping a tooth would leave it behind, clcokwise of #1. Unless like half the sprocket has no teeth and it totally was spinning free and grabbed the sprocket again at a random orientation, but that'd be REALLY crazy stuff.

I don't mean to labor the point- it's just been my experience that monkeying without a diagnosis makes it impossible to diagnose. If I'd played with the distributor, then I wouldn't be able to see if the timing appeared "off" because the rotor position was monkeyed. Plus, well, timing chain's an ugly SOB to get to, I can do it but I need to KNOW it's the problem and the fact that it's not that old and the lack of apparent slack is a problem here.

I am inclined to bend that rule and replace the PIP and the TFI though. Just... because I'm running out of things to do.

I did see a lot of people say that since the TFI has been so failure-prone due to distributor heat, they moved it to in front of the engine and ran wires back to the dizzy. Neat.... might have to do that, but not until I already have this running again.

Oh yeah, duh- the distributor rotor doesn't point perfectly at the #1 dist cap stud because the dist housing is rotated where it is for timing adjustment. If TDC lines up with #1 stud exactly, the dist was rotated so the #1 stud and its firing trigger is ahead- clockwise- of the rotor at TDC so it fires 10 deg BDC. It's exactly where it should be, I think.

 

Found a reference online that if SPOUT is removed, it falls back on the PIP sensor to time the sparks. Still plenty of spark, but no ignition.

Pulled out spark plug, put my finger over the hole, cranked. Nearly pulled my finger off, and blew it out. Continuing to crank I felt air blast on my leg a couple of feet away. FWIW. Replaced the plug.

Opened up the throttle body and added a load of carb cleaner. THAT OUTTA DO IT. That stuff doesn't need compression to fire. No, it STILL doesn't fire.

There's absolutely nothing wrong with this engine, aside from the fact that it doesn't run.

 

It tried to suck your finger in? i wouldn't think it would have that much vacuum if the intake was opening.

if you set the crank at whatever you have your timing set to the dizzy should point to #1, a 1/4 of the way to the next stud is 40 degrees (cam is 1/2 of the crank, so 180d/4)

and yeah with the spout removed it goes to just base timing, which is why you disconnect it when you set the timing.

i agree about working without a diagnosis.
Ford Ranger/Bronco II TFI Ignition Diagnostics

maybe a compression test too just so you can at least say that you did...

 

I didn't have the pedal down at the time, so I would expect notable vacuum there.

Hmm, let's see. A full crank rotation is 360 deg, there's 1/2 rotation of the cam per crank, and 8 studs per cam rotation. So it's 90 deg of crank from stud-to-stud. Hmm, I was only ballparking it but the rotor does seem further than it should be, but there's just no timing chain slack making a problem for the jumped-time thing.

Compression test is not a bad idea to rule out cam problems- but it's gonna be half a day to get a ride over to the parts store to get one...

 

yeah, I was pondering if it felt like it the valves weren't open at all, and trying to suck it all in through the spark plug hole.

 

compression test can also tell you if timing is off. I did a compression test on mine when it wouldn't start,all were well below 100 psi,I thought the motor was done,that is when I moved the dizzy,the engine started,retested the compression,numbers were good for an engine with 160,000 miles on it. I know you said you don't want to move the dizzy,but you can mark it before you move it,so you can move it back to where it was if you want to,that is what I did.