Hard cold start

BAOSBORNE

MEMBER
FORD BRONCO

I have a 1990 full size Ford Bronco, 5.8, about 100000 miles. After it sits overnight it doesnt want to start. When I turn the key on, the fuel pump comes on and runs continously for a few minutes then shuts off which the will allow the engine to start. Fuel pressure comes up instantly as soon as the key is turned on. I've replaced the cold start valve, dist cap and rotor, coil spark is good, checked fuel pump relay with one from friends ford, checked for loose or dirty grounds. After it finally starts, it works fine all day with no problems. Thanks for any help :

9 Replies

MERLIN2021

MECHANIC
17,250 POSTS

Could be time for a new pump, before you start it in the morning test the key on pressure, then running pressure, the pump should only run for 4-5 secs! With key on engine off.

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Saturday, September 22nd, 2007 AT 6:24 PM

BAOSBORNE

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Thanks for the info but I did all of that everything was within specs, I'm kind of leaning towards a possible bad sensor, don't know which one would cause this problem though, possible bad ICM as I'm getting good fire from the coil or possiblily a bad PCM, sending a false signal to the pump. I was hoping someone might have had this same problem. I sure like working on heavy construction equipment better, it doesn't bend when you hit it with a hammer!

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Saturday, September 22nd, 2007 AT 7:44 PM

FISHERMAN

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937 POSTS

I`m agree with Merlin.
If the pump its running more than a few seconds that means that the pump its not reaching the proper pressure on the fuel rail.

Hear the pump "whinning" doesn`t mean its working right.

Did you check the gas pressure?
How many PSI did you get?

Let us Know!

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Wednesday, September 26th, 2007 AT 10:05 AM

BAOSBORNE

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Yes, I ran all of the pressure tests, 40 psi engine off and 34 psi engine on, also performed a volume test that also was well within specs, I agree it sure sounds like its the fuel pump and as its a module type, looking at the schmatic it could possibliy be the shuttle valve malfunctiong in the module, I don't know, but due to the expense of the module and the labor to drop the fuel tank, a real pain in the you know where, I was hoping this had happened to someone else. Lets face it, I'm a retired heavy equipment mechanic and my old bones relly don't want to crawl under this thing if I don't have to, and I really do apprecaite all of the help. Thanks, Bruce

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Wednesday, September 26th, 2007 AT 11:00 AM

FISHERMAN

MECHANIC
937 POSTS

Well. Looks like you are focusing on "fuel" but if your pressure its right.
Are you sure that the engine its running "dried" when cranked in the morning?

Could be something simple.

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Wednesday, September 26th, 2007 AT 2:19 PM

BAOSBORNE

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If you mean dried as the system bled down over night, yes, when I first hook the pressure gauge to the system, theres no pressure until I start cranking the engine and then it comes up imediately, but I'm wondering now if I might be getting an air lock in the system, is this possible on a gas engine thats fuel injected?

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Wednesday, September 26th, 2007 AT 4:38 PM

RASMATAZ

MECHANIC
75,992 POSTS

Just got your PM 1min. Ago-okay hook the pressure gauge up and run the engine for a minute shutdown and monitor the pressure for atleast 8 minutes-like the fisherman said running dry.

When the pressure drops fast, you have residual pressure leak. Check the regulator, fuel pump check valve, & injector/s leakdown.

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Friday, October 26th, 2007 AT 10:06 PM

RASMATAZ

MECHANIC
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Inbox : Message
From: baosborne
To: rasmataz
Posted: Fri Oct 26, 2007 10:50 pm
Subject: cold hard start

I understand what you mean about the fuel pump and check valve, but it takes all night to bleed down and ford specs say that will happen at least the book I have does. There should only be about 5 psi in the morning. Question, after the pcm runs it self check when the key is first turned on, does the pcm also shut the power off to the fuel pump relay or is that relay turned off from the icm. As I said, this only happens once a day.

The PCM powers the fuel pump and inertia cut off switch. Once the fuel pump de-energizes the ICOS takes over the fuel pump. Something like the Chevy's fuel pump/oil pressure sending unit.

The pump takes its power from the starter relay blue fusible link and also the distributor red and light blue also at the starter relay.

Might want to test out the EEC power relay and also the ICOS. Also check the fuel pump ground circuit.

Its funny though I got all the information about the electronic engines controls but no fuel pump circuit-The only wire that goes from the inertia switch is the brown wire which I assume that's the wire that powers the pump. Correct me if am wrong with this.

When it hesistates to start check for injector pulse.

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Saturday, October 27th, 2007 AT 2:24 AM

JWALTH02

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180 POSTS

Not to jump in way too late but I'll throw in my two cents. When you say cold start how cold is it? Where about are you living?

I ask this because I have a 92 bronco with the same motor, and when I bought it, it looked like the stock battery :) but that was living in salt lake where the coldest it got was 15 degrees. Now I live in Wyoming where it stays -20 and the wind chill is -45 for weeks at a time. The truck refused to start. I put in a block heater and that helped a bit but it would have the same problems you're having. I bought an Optima yellow top battery and have had NO problems starting since. Get your battery tested if you haven't already.

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Friday, November 2nd, 2007 AT 6:38 PM