Author Topic: no fuel tbi ::solved  (Read 21821 times)

Offline Irish_Alley

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Re: no fuel tbi
« Reply #30 on: December 03, 2014, 12:43:43 PM »
On a side not I can still hear both pumps prime when each tank is selected. But the right one won't start the engine could be out of fuel but I haven't used the couple gallons in it.
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Irish_Alley

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Re: no fuel tbi
« Reply #31 on: December 03, 2014, 07:58:24 PM »
OK so I took it home with the egr solenoid unhooked. Didn't stall once. Got to the shop turned it off cleaned up the trailer and turn the key over. No fuel pump prime but it will start if it cranks a couple more seconds. The tank that wasn't running right turned out to be empty some how so that solved.
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline VileZambonie

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Re: no fuel tbi
« Reply #32 on: December 03, 2014, 08:23:04 PM »
I was just going to ask if you had gas in it. You really need to do the pinpoint tests on the fuel pump relay circuit.


 When the key is first turned ON, without the engine running, the ECM will turn the fuel pump relay ON for two seconds. This builds up the fuel pressure to normal operating pressure. If the engine is not started within two seconds, the ECM will shut the fuel pump OFF and wait until ignition reference pulses are present. On heavy duty models, a fuel module will override the ECM and the fuel pump will operate for approximately twenty seconds. This corrects a hot restart (vapor lock) during a high ambient temperature condition. As soon as the engine is cranked, the ECM turns the relay ON, which powers the fuel pump. The ECM continues to power the fuel pump during engine operation. If the fuel pump relay fails, it is backed up by the oil pressure switch, which continues to operate the fuel pump as long as oil pressure remains above 28.0 kPa (4 psi).


•A faulty fuel pump relay can result in long cranking times, particularly if the engine is cold.
•An inoperative fuel pump would cause a no start condition. A fuel pump which does not provide enough pressure can result in poor performance.


 CHART A-5 - FUEL PUMP RELAY CIRCUIT DIAGNOSIS (ONE FUEL TANK)

CIRCUIT DESCRIPTION :

 When the ignition switch is turned "ON", the Electronic Control Module (ECM) will turn "ON" the in-tank fuel pump. It will remain "ON" as long as the engine is cranking or running, and the ECM is receiving distributor reference pulses. If there are no reference pulses, the ECM will shut "OFF" the fuel pump within 2 seconds after ignition "ON" or engine stops except when a fuel module is used.

 The pump will deliver fuel to the TBI unit where the system pressure is controlled to about 62 to 90 kPa (9 to 13 psi). Excess fuel is then returned to the fuel tank.

 A fuel module is used on all 7.4L, G van with 5.7L, and all other 5.7L over 8500 GVW engines to correct a hot restart (vapor lock) during a high ambient condition. It is designed to over-ride the ECM two second pump operation and will run the fuel pump for twenty seconds at initial ignition "ON".

TEST DESCRIPTION : Numbers below refer to circled numbers on the diagnostic chart.


1.This procedure applies direct voltage to run the fuel pump. If the pump runs, it may be a fuel pump relay circuit problem which the following step will locate.
2.This step checks voltage from the battery and the ground circuit to the relay.
3.This test determines if there is voltage from the ECM, terminal A1, to terminal "D" on the relay connector.
4.This completes the fuel pump relay circuit but if this diagnosis was used because the engine would not run then oil pressure switch should also the diagnosed.

DIAGNOSTIC AIDS :


•An inoperative fuel module may be the cause of a hot stall/no start condition. Check for power and ground circuit to the fuel module and a complete circuit to the pump from terminal "A". If OK, and the pump does not run for the specified 20 seconds at initial ignition "ON", replace the Fuel Module.
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Offline Irish_Alley

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Re: no fuel tbi
« Reply #33 on: December 03, 2014, 08:39:50 PM »
This is going to be fun. I checked the connection at the ecm it was clean no signs of moisture/rust. Turned key on still no prime. Turned key off and swapped fuel pump relay with another used one. Pump primes and starts. Swapped relays again so the "bad" on was in and it stilled primed.
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Irish_Alley

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Re: no fuel tbi
« Reply #34 on: January 09, 2015, 08:21:33 AM »
been a while so i figured i do a little update. no problems since it stalled at the dump a couple months ago. but the pump would sometimes prime and sometimes not prime. then if i switched tanks while running it would stall out and not start back up till i messed with the tank switch.

 i ordered one from napa and went to put it in right in their parking lot and once i removed my old one it was so hot it scared me a little and i dropped it lol. wasnt real hot just wasnt thinking it would have any temp to it. swapped switches and she primes herself when you turn the key on all the time now and no more stalls when switching from one tank to the other
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes