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Juan Crespo
Juan Crespo, Tech Trainer
Category: Ford
Satisfied Customers: 1513
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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1990 5.8L Bronco. Will not start all the time. Changed coil,

Customer Question

1990 5.8L Bronco. Will not start all the time. Changed coil, plugs, cleaned injectors. tested relay, changed distributor and module. When it does start it will Idle just fine but will eventually drop RPM to zero than back to normal
JA: Does the engine turn over? How old is the battery?
Customer: new battery, Turns over just fine
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: The list above is what I have replaced. I also tested fuel pressure and even changed the fuel pressure regulator.
JA: Anything else you think the mechanic should know?
Customer: Not that I can think of
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Ford Mechanic about your situation and then connect you two.
Submitted: 5 months ago.
Category: Ford
Customer: replied 5 months ago.
No computer error codes
Expert:  roy replied 5 months ago.

good morning my name is ***** ***** I will assist

the first thing I would do is check the fuel pressure. it sounds like you may have a failing fuel pump. you can rent a tester at a parts store to verify.

have you done this yet???

Roy

Customer: replied 5 months ago.
steady at 36 PSI
Customer: replied 5 months ago.
Some blogs I have read has me thinking the TPI is failing or corroded. Could this have something to do with it. I got it running last night. Mechanically sounds fine but will drop RPM from 600 to zero and back to 600. As it warms up the RPM will adjust accordingly but will still momentarily hesitate than back to normal. Put in gear and it stumbles and even quit several times. Got it moved about 20 ft with a lot of restarting that was surprisingly starting immediately like it should but would stumble in gear and barely recover when shifted to neutral.
Expert:  roy replied 5 months ago.

ok, 35-45 is the spec

is this with the engine running or off??

Roy

Customer: replied 5 months ago.
Running. I didn't measure it off. I can recheck it. I changed the fuel pump a few years ago. Could it be running erratically? The Bronco would sit for several weeks at a time for the last couple of years. Before that no problems while it was a daily driver
Expert:  roy replied 5 months ago.

yes, it could. slao, did you change the fuel filter??

Roy

Customer: replied 5 months ago.
fuel filter was changed
Expert:  roy replied 5 months ago.

did you see the condition of the fuel???

if the pressure is good, although it is borderline, I am wondering about the injectors. adding cleaner does nothing for cleaning.

Roy

Customer: replied 5 months ago.
Fuel was clean. I even pulled the injectors and cleaned them. They didn't need it but I did it anyway. The fuel was fine. I dumped the filter contents in a glass jar to if there was any water condensation but it was clean and water free. I even pulled the throttle body and cleaned it since I had to move the intake to get to all the injectors. I was mainly looking for a dead, or cracked injector but they passed with flying colors. I followed an injector test found in the service manual. I don't remember the readings. I didn't write it down
Expert:  roy replied 5 months ago.

ok, how about the ignition timing????

Roy

Customer: replied 5 months ago.
Timing was reset when the Distributor including internal electronics and module on the side of the Dist. was replaced. No change in the results so that ended up a dead end.
Expert:  Juan Crespo replied 5 months ago.

Hi there. Different expert here.

The key to this diagnosis is to first determine what's missing when the engine won't start; is it fuel pressure, injector pulse or ignition spark.

I do understand that many parts have been replaced, but we can't overlook the possibility of an intermittently bad connection somewhere causing this no-start condition.

Can you check that and let me know?

Customer: replied 5 months ago.
From an earlier email I asked him if the TPI and fuel pump connections could be corroded, dirty etc could be the cause. I didn't get an answer and still need to check these. The connections of all the replaced items connectors were checked and cleaned even the brown relay connection was checked and cleaned. The relay was even changed but put back on when no change occurred. Can't remember the computer acronym off the top of my head at the moment for the brown relay computer it engergizes. Is there any particular wire circuit(s) I should look further while I am under the hood cleaning the above listed items?
Expert:  Juan Crespo replied 5 months ago.

OK. You are now working with a different expert.

Let's not get ahead of ourselves. Instead, let's find out what is missing when the engine won't start. Once we know that, then we'll go ahead and pinpoint the issue.

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