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Strange 'no start' issue...

7K views 60 replies 18 participants last post by  JuiceBronco17 
#1 ·
'90 model Bronco, 302, AOD

Coming home from work a couple of days ago...bronco starting losing power, backfiring, running rough...finally died. After about 10 minutes on roadside I tried to crank it. It started up (ran rough...then cleared up) went about 2 miles then started running poorly again, died.

This continued several more times until I finally made it home. Got a ICM and installed on the distributor, cranked up motor it ran fine for a test drive. Next morning the Bronco would not start (cranks fine).

Figured MAYBE the distributor pick-up was bad (dizzy is old), replaced...no start. Coil is old...so replaced it, no start.

Yes...I know, "throwing parts at it" is ill advised, but these parts were old and I have very little time to do much in depth testing on it. I will pull some codes later on....but what are some 'common' reasons for a no start condition.

Fuel pump is new (this past summer it went out), I can hear it priming up fine...but haven't checked the pressure yet. IAC and EGR are new. TPS hasn't been giving any trouble.

When I pulled spark plug last night and grounded it out...there was spark...but it looked kind of weak. Yellowish, not a good blue spark.

Any ideas where to start from here will be appreciated.

Flint.
 
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#4 ·
Not entirely out of the question...but it is only a couple of months old and it wouldn't explain why it went from running fine (the night before) to a 'no start' the next morning.

However...if it proves to be 'fuel' issue rather than a 'spark' issue ....I will certainly look at the filter.

Thanks for your reply,

Flint.
 
#3 ·
Flint, you sound like you are fairly mechanically inclined so forgive me if I suggest things you've already crossed off your list. But think basic, your truck needs fuel, air, and spark. If it has these things with no problems relating to them it should light. Sometimes when Im stumped I just make sure to check these basics before I get tied up with more complicated things. Check spark at the wires. Check fuel pressure. Even double check the firing order since you have been there. And while checking plugs I like to take the time to check the compression while Im there. May not solve your problem but sometimes poking around with the basics can lead you to an underlying problem.
 
#5 ·
Black'nTan96 wrote:

But think basic, your truck needs fuel, air, and spark. If it has these things with no problems relating to them it should light.
Agreed. Just trying to decide which to look at first. I'll pull some codes tomorrow and see if that will help steer me in the right direction. It could be something as simple as a wire going to ground.


Sometimes when Im stumped I just make sure to check these basics before I get tied up with more complicated things. Check spark at the wires
.

I had pulled one wire (and plug) grounded it and cranked the engine (quick way to check for spark) but it looked a bit weak to me. Stalling and sputtering engine (if spark related) is classic Bronco ICM or Distr. Pick-Up, so that is why I changed the ICM (I carry a spare). That actually seemed to cure the problem. Odd that the vehicle would not 'fire' the next morning.

Distributor problems can be intermittent and mine was very old, so no skin off my nose replacing it. Pretty sure...I've got the firing order right and didn't get the distributor put back in 180° out. Even then...it should TRY to fire.

New coil...just to ensure good spark, cheap part.


Check fuel pressure
I'll check that tomorrow. I've got a gauge. New fuel pump this past summer, new injectors (just maintenance at same time). Has new IAC and EGR (all old items...I was slowly replacing). TPS is a few years old...but checks out.



Thanks,

Flint.
 
#6 ·
Are the plugs wet with fuel? I had similar symptoms with my truck when I bought it and drove it home. Ended up being a bad ECT. Pull codes. Takes 5 minutes. Then see what if any pop up. G/L
 
#8 ·
Is it failing to start again after running (or even after sitting and cooling down)? Mine would stall and re-fire while driving, and then a little while later it would only start after cooling down. Then, after trying fuel filter, distributor ICM, ignition coil, testing all wires, I gave in and took it to my a local mechanic. Turns out the Ignition module (NOT the ICM on the dizzy) has a heat sink that corodes over time, and the heat wont transfer from the Ignition module to the heat sink.

I had it replaced once at the first mech, but then it began again several weeks later. Took it to a recommended mech and he found the rust on the heat sink. He cleaned up the heat sink, and put some heat transfer goop between the sink and the module. The total job (with motorcraft part) cost about $300. WELL WORTH the $$$, considering the parts I didnt throw at it.

Motocraft part number 1x226 (what was on my invoice)
PArt cost 219.36

THe one the first mech put on was chinese and cost about 90.00. AVOID IT. The second guy said the orginal Ford part lasted probably 4 to 5 years even with the overheating/heat sink corrosion. The first replacement Chinese part took a crap in a week...

Hope that helps. Its a very common 302/351W issue by the looks of the threads...
 
#10 ·
Double checked firing order: Good

Fuel pressure (at prime up) 38-40 psi.

Checked all wires and connections for obvious breaks, chaffing, or disconnected fittings/connectors. All looked fine.

Pulled # 6 plug and wire (easy to get to), grounded it and cranked the engine. Got a spark..but still doesn't look exactly right to me. Sort of yellowish/orange, not a good blue spark...but there is 'spark'.

Got some codes: 33, 84, 52 and a separator code. Don't think any of these would prevent the engine from starting?

Had one event when reading the codes (vehicle not responding), but when I ran it a second time it worked (ECM)?

Dunno guys...it has me stumped.
 
#13 ·
How old is the ignition switch......just on the odd chance test it and I don't think old fuel filters will prevent a vehicle from starting unless they've been "fouled" by water or mud from off roading etc. ...though it can't hurt to change them if they haven't been done for a while...

Sounds like the FPR = fuel pressure regulator is ok with those psi numbers, any issues with injectors.....IDK

You said you replaced the distributor and ignition module, was it a TFI = thick film integraded style...did you test the old one, several times for passing grade before replacing...

Does the 90 BKO have a PIP = profile ignition pickup on the distributor shaft.....?

Definately test the EVP sensor that sits on top of the EGR valve and see what you come up with, maybe it needs to be replaced if it's been on there for a while based on the fault codes.

ECT = engine cooling temp sensor is a fuel manager at cold start and normal operation but any issues with it can prevent the engine from starting, rich condition etc. etc.

Is the alternator putting out enough voltage....?

Just a few thoughts!

Good Luck ~ :thumbup
 
#14 ·
JKossarides wrote:

How old is the ignition switch......just on the odd chance test it
Brand new this summer, actuator broke...but I replaced the switch at the same time.


and I don't think old fuel filters will prevent a vehicle from starting unless they've been "fouled" by water or mud from off roading etc. ...though it can't hurt to change them if they haven't been done for a while...
Fuel filter only several months old, no bad fuel through the tank...that I know of. New fuel pump recently, good fuel pressure, its getting fuel (but perhaps in various amounts).

Sounds like the FPR = fuel pressure regulator is ok with those psi numbers, any issues with injectors.....IDK
Injectors are new....less than a year, been trying to slowly get new parts on the old bronco...bit by bit.


You said you replaced the distributor and ignition module, was it a TFI = thick film integraded style...did you test the old one, several times for passing grade before replacing...
Yes TFI (gray) same type I've running for 20 years. No...didn't check, I keep a couple of spares at all times.

Does the 90 BKO have a PIP = profile ignition pickup on the distributor shaft.....?
Yes, new with new distributor, cap and rotor.

Definately test the EVP sensor that sits on top of the EGR valve and see what you come up with, maybe it needs to be replaced if it's been on there for a while based on the fault codes.
Both parts new...this summer. Also new IAC

ECT = engine cooling temp sensor is a fuel manager at cold start and normal operation but any issues with it can prevent the engine from starting, rich condition etc. etc.
Hmmmmmm....could be a problem.

Is the alternator putting out enough voltage....?
Yes...good 160 amp alternator, good strong battery.

Just a few thoughts!

Thanks for your input Sir.

Flint.
 
#20 ·
New ECT, still no start.

Specifically, what items/conditions could cause this?

I know I'm getting fuel to the fuel rail (40 psi), I assume my injectors are working (they were the night before the engine wouldn't start). I've established that I am getting spark (even though I think it a bit weak).

No obstructions to prevent air from getting to the engine.

Fuel + Air + Spark = Engine start (or at least trying).
 
#22 ·
Agreed, but it didn't suddenly lose compression on several cylinders (which is what it would take to not start), overnight...with the engine just sitting there. ;)

Remember, the engine was running fine (on test drive) just hours earlier, but would not start the next morning. Hence the "strange" label in my opening post.
 
#23 ·
starting issues

sorry if im posting in the wrong place ...i'm new to the site.


need immediate help.. i have an 89 351 5.8 and i had my belt break which caused me to overheat and blow the hose on the radiator...got my buddy to tow me home, i replaced the radiator and belt and now its not starting its turning over but not firing any ideas.

thanx
 
#24 ·
Subscribed.

Sounds like we're in the same boat...except that mine will start once and only once if it's been sitting for like a week. Here's my thread on that.

I've been through all the same stuff you have.

I'll let you know if I figure mine out.
 
#25 ·
I'm leaning towards the EEC at this point. I am going to double check all my grounds and connections, but I've had various symptoms in the past that make it suspect....I.E. continuous running of the fuel pump, weird codes, (vehicle not responding) prompt when checking codes.
 
#26 ·
Yeah, I tried swapping my EEC too but without any luck. I had little hopes that it would change anything but I wanted to get a manual computer anyways so I figured I'd kill two birds with one stone.
 
#34 ·
Well.....crap, looks like I spoke too soon.

Bronco is now starting, but I had trouble again today going to work. The new EEC let it start right up, I used it around the ranch yesterday (short distances), no problem.

This morning I got about 10 miles towards town and it started losing power, popping back back through the intake...then eventually died (just like the initial problem). Let it rest for about 15 minutes, it will start back up, run rough for 5-10 seconds, smooth out....but only go about 2 miles before it craps out again.

New:

EEC Relay
EEC (computer)
Distributor and ICM
Cap and Rotor
Coil
Plugs and Plug Wires
ECT

Recent:

Fuel Pump
EGR valve
IAC


Older Parts:

O2 sensor
TPS
MAP

Almost acts like a back pressure issue (catalytic converter, muffler). I don't know, this one has me stumped.
 
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