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I have a 1987 F150 4-wheel drive 4.9 L manual transmission…

I have a 1987 F150...
I have a 1987 F150 4-wheel drive 4.9 L manual transmission Federal emissions. Driving home from the gas station one day it started running rough I barely made it home it quit in the driveway will not restart. The fuel pump continuously runs with the key in the in the Run position the injectors will not pulse they have a steady 12 volts on both wires in and out of the injectors there is fuel pressure at the rail 55 PSI and I have spark. If I disconnect the fuel pump relay the fuel pump stops when the key is in the Run position. The same thing goes for disconnecting the eec relay. I am suspecting a bad ECM. Is there a way to verify the ECM is bad before sending it out for R&R? I have removed the cover on the ECM and looked at the capacitors they don't seem to be leaking there doesn't seem to be any discoloration in the circuit board itself and no corrosion on the board or on any of the pins on the ECM itself or the 60 pin connector. In addition to this I cannot communicate with the ECM for any trouble codes the engine light does come on with the key in the Run position and the tachometer does move when cranking.
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Answered in 3 minutes by:
2/22/2018
kalamykid
kalamykid, Shop Owner/ Tech
Category: Ford
Satisfied Customers: 5,511
Experience: I HAVE OWNED MY OWN SHOP FOR OVER THREE YEARS. I HAVE THE TOOLS AND SOFTWARE TO ANSWERE ALMOST ANY Q
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Before you go replacing the ecm, have the ignition module checked at your local auto parts store. The ignition control module tells the computer when to fire the injectors. Even if you have spark, the icm can be bad.

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Customer reply replied 4 months ago
This has the thick film integrated module located on the distributor. Pip signal is present when cranking therefore I don't believe the TFI module is the culprit here unless there is something I am missing about it. Also how would a defective tfi affect the continuous running of the fuel pumps and cause no interaction between scan tool and ecm. Interaction with ecm was existant prior to this problem.

I did not know the ecm would not connect to a scan tool. Have you checked all your fuses to make sure you do not have any that are blown?

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Customer reply replied 4 months ago
I have checked all the fuses. I guess my main question is is there a way to verify 100% that the ECM is the culprit?

Not with out a break out box, or installing another known good computer. This year truck doe not have to have the ecm programmed, so you can install a good used computer.

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We can however test a few sensors and see if the voltages are correct for them. If the voltages are wrong, then I would lean to a bad ecm.

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Customer reply replied 4 months ago
It is asking me to update my payment info I just put my payment info today there's nothing to update. Also I have checked for five Holt reference on the throttle position sensor the EGR and the map sensor with key on they all have 4.9 volts. Is there something else I need to check?

You asked for a live phone call and that is why it is asking for you to update you card information. There has been a problem with the site, and they are trying to fix it.

See what the voltage is to the dpfe please.

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Customer reply replied 4 months ago
The dpfe registers 5 volts also. What are your thoughts at this point?

I still think the ignition module is your culprit. Can you remove it from the distributor and have your local auto parts store test it please?

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Customer reply replied 4 months ago
I will have to see if any of the local parts stores are even capable of testing it first. I did already test it using my Rotunda# ***** TFI-IV Ignition testor with PIP and Tach confirmation and it passes.

Let em know if you have a parts store that can test it. Make sure they run the test 5 times to fully warm up the module. If it fails any of the 5 tests, replace it.

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Customer reply replied 4 months ago
I haven't found any place in milwaukee that is capable of testing it. They all say it's too old. I've checked 12 different parts houses, napa, O'Reilly's, Autozone, carquest, advance, federated, and even 3 ford dealers. The ford dealers have the same tester I do. It'll be cheaper to throw a new one at it. My gut feeling is ecm but I will put a new tfi in tonight and see what happens. I know the tfi tells the ecm when to pulse the injectors but I don't see how it can affect the running of the fuel pump(s) because the ecm only grounds the relay for the pump. Also the no- communication with ecm isn't a byproduct of a bad tfi. Note: With tfi disconnected, and key in run position-fuel pump still runs continuosly. I will let you know what hapoens.

This is a tough one to deal with, but an ecm is t expensive to put had not solve the problem. On this truck the fuel pump will run as long as the ignition switch is in the run position. That is why Ford uses an inertia switch.

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Customer reply replied 4 months ago
You mean the fuel pump is capable of running continuously with key in the on position. It is not designed to do so. All the fuel pump needs is a ground some where-wether it's the tan with light green striped wire ftom fp relay being grounded by ecm or a short to ground by same wire, or an internal grounding by ecm.

Yes the fuel pump system on this truck will stay active if the ignition switch is in the run position. As a safety precaution ford installed the inertia switch so the pump would be cut off if the vehicle was involved in an accident.

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Customer reply replied 4 months ago
Well put in a new tfi and no dice. Now having a hard time finding a replacement ecm. None of the parts supply houses have a listing for my particular ecm. Looks like I'm gonna have to send mine in for repair.

What is the number on yours?

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Customer reply replied 4 months ago
Sent computer in for repair to G7 computers in Henrietta New York.
Was not repairable. The was an ip chip that had a burnt spot along with some other components that were bad. The other components were replaceable, the ip chip is obsolete-therefore rendering ecm useless. They sent it back to me no charge. I did some research on the company in the link you sent me with the ecm for sale on Ebay. Not many good reviews about this place (All Computer Resources) I had decided to try FS1. I should have replacement ecm by weekend. Will let you know how it turns out.

Thank you for the update.

kalamykid
kalamykid, Shop Owner/ Tech
Category: Ford
Satisfied Customers: 5,511
Experience: I HAVE OWNED MY OWN SHOP FOR OVER THREE YEARS. I HAVE THE TOOLS AND SOFTWARE TO ANSWERE ALMOST ANY Q
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Customer reply replied 4 months ago
Update: New (replacement) ecm from FS1 arrived yesterday. I installed and exact same symptoms. I decided to start from square one. Checked for spark-yes. Checked fuel pressure at rail-yes and 55 psi. Still no communication with ecm through my solus. Here's the new dexelopment: As before, I checked to see if it was actually getting fuel by spraying starting fluid in the intake tubes and there was an initial fire up for about ten seconds. However my helping decided to work the throttle a bit and it stays running! But here's the tricky part- with replacement ecm it idles at 2000 rpm and won't come down. With original ecm (which I was told by G7 computers was bad) it'll start with the aid of starting fluid and stay running on it's own but at a low (almost normal) but horribly galloping idle. Sometimes it even dies but will restart. If you leave truck sit for an hour or overnight it won't restart without the aid of starting fluid. Another new development-you can't rev it up normally because it will just bog down like not getting fuel. If you ease throttle up slowly you can attain high rpms. This truck has me stumped. Why will it start with starting fluid but not on it's own?? When it just cranks(no start) there's no injector pulse but when you spray starting fluid and get it running the injectors are pulsing.(obviously) Where do I go from here?
Customer reply replied 4 months ago
Forgot to mention fuel pumps still run contiuously with key in run pistion. Fuel pump relay is working correctly.
Customer reply replied 4 months ago
I was re-reading our previous conversation and I noticed perhaps that I may be unclear on something: Should the fuel pump be running contiuously with key in run position and engine not running? I was under the impression it's on a timed cicuit (1-2 seconds) when the key is first turned to run and then doesn't run again til engine is being cranked. Am I wrong?

Sorry for the delay. Yes the fuel pump on this truck will run as long as the key is in the run position.

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