Will not start

[randy merritt]

Re: Will not start

Why would this happen? Mine is doing this. I have a leak somewhere in the fuel system. If I get it to start, shut it off and start it before it leaks down, it will fire right up. It's never ending with this thing.

My understanding of this is that the oil pressure sensor will send power to the fuel pump once enough oil pressure has built up from extended cranking, but this is a question better answered by those with more knowledge than myself. I may be way off base in my understanding.

 

[Damian]

Re: Will not start

My understanding of this is that the oil pressure sensor will send power to the fuel pump once enough oil pressure has built up from extended cranking, but this is a question better answered by those with more knowledge than myself. I may be way off base in my understanding.

Makes sense. Mine won't even kick on to prime the system now.

 

[Don W.]

Re: Will not start

Fuel pump should run for 2 seconds with key on, Then once motor running it stays on of course. I've heard the oil pump theory many times. I ran my truck for a year with the oil pressure sender disconnected so something else makes the fuel pump run. I'll look that up.

With the two second run with the key fuel turn key off and pressure should hold from there with virtually no noticeable drop. Vac/pressure line to the FPR is gonna make virtually no difference in fuel pressure because there is very little vac when cranking. Once running FP will drop some because there is now vac on the FPR. Set fuel pressure with motor idling and vac line off.

 

[Don W.]

Re: Will not start

Well I looked this up. With key on the ECM activates the FP relay for 2 seconds. With key in the start position the ECM activates the FP relay while starting. Once the ECM detects a run condition it also activates the FP relay. The oil pressure sender is a backup if there is a failure somewhere with the ECM. With oil pressure a switch is closed in the sender which will also keep the FP relay closed.

You can test all this by measuring voltage at the test lead near the dist. Key on should show bat voltage for two seconds. Key in start should show continuous voltage and once running the same. You can check to be sure that the ECM is keeping the FP running, and not the oil pressure sender, by disconnecting the oil pressure sender harness at the sender. No easy to do.

Hope this clears things up a bit.

 

[grimprime221]

Re: Will not start

Well I looked this up. With key on the ECM activates the FP relay for 2 seconds. With key in the start position the ECM activates the FP relay while starting. Once the ECM detects a run condition it also activates the FP relay. The oil pressure sender is a backup if there is a failure somewhere with the ECM. With oil pressure a switch is closed in the sender which will also keep the FP relay closed.

You can test all this by measuring voltage at the test lead near the dist. Key on should show bat voltage for two seconds. Key in start should show continuous voltage and once running the same. You can check to be sure that the ECM is keeping the FP running, and not the oil pressure sender, by disconnecting the oil pressure sender harness at the sender. No easy to do.

Hope this clears things up a bit.

Thanks for the great info. I tested the lead using a test light between the lead and a hot positive (not sure if this is the correct procedure) and it has power (light lit) but with key to start and engine cranking the light goes out, a few seconds after I stop the light comes back on. Not sure if this indicates fp failure or ecm failure or some other problem or I just tested it wrong.

 

[Quickstop [UK]]

Re: Will not start

just bypass that circuit. Small spade connector to the FP test lead from the 12v block on the firewall and you'll have power to the pump the whole time.

 

[Quickstop [UK]]

Re: Will not start

Can you recap where you are?

As I understand, with ether, it starts. So compression, spark and timing are ok.

Have you checked your injector harness? Key in, engine off, you have 12v on both terminals. Just disconnect an injector. The ECM grounds the injectors so if it's not working, you'll have FP and no spray.

Any codes on your ECM? Specifically code 12 (a test sequence).

 

[Don W.]

Re: Will not start

Thanks for the great info. I tested the lead using a test light between the lead and a hot positive (not sure if this is the correct procedure) and it has power (light lit) but with key to start and engine cranking the light goes out, a few seconds after I stop the light comes back on. Not sure if this indicates fp failure or ecm failure or some other problem or I just tested it wrong.

You're backwards. To do what I'm talking about your light or meter goes between the test term and ground.

 

[grimprime221]

Re: Will not start

Rechecked the fp and had power the whole time when cranking. going to try the injector test I got the test kit.

Still starts right up with ether and runs great after but wont start on its own. has about 47 psi cranking fp pump has power based on test lead ignition module is new. scanner didn't show any codes.

 

[Don W.]

Re: Will not start

Rechecked the fp and had power the whole time when cranking. going to try the injector test I got the test kit.

Still starts right up with ether and runs great after but wont start on its own. has about 47 psi cranking fp pump has power based on test lead ignition module is new. scanner didn't show any codes.

That 47# FP is about 10# high. Just for the heck of it try starting with the pedal to the floor.

 

[grimprime221]

Re: Will not start

That 47# FP is about 10# high. Just for the heck of it try starting with the pedal to the floor.

doesn't make a difference if its to the floor or not

 

[Don W.]

Re: Will not start

Didn't think it would but worth a try. Flooring it puts it flood mode and doesn't fire the injectors. Without going back and reading the entire post have you changed the dist module?

 

[grimprime221]

Re: Will not start

Didn't think it would but worth a try. Flooring it puts it flood mode and doesn't fire the injectors. Without going back and reading the entire post have you changed the dist module?

if by ignition control module then yes brand new

 

[Don W.]

Re: Will not start

I imagine you've done this already but if not check the ground on the back of the head, drivers side. There should be 2 wires going into 1 terminal. Also there should be woven copper ground strap from there to the firewall.

 

[grimprime221]

Re: Will not start

I imagine you've done this already but if not check the ground on the back of the head, drivers side. There should be 2 wires going into 1 terminal. Also there should be woven copper ground strap from there to the firewall.

i'll look but runs with the ether so didn't think that

 

[Quickstop [UK]]

Re: Will not start

Have you got some NOID lights? See if the injectors are actually opening. Have you got a spare ECM?

Are they stock injectors?

 

[Don W.]

Re: Will not start

The manual for a crank but won't run diagnostic is 7 pages long. Since I kinda know what you've done so far I'll try to summarize. Some of these may have been asked and answered. Verify or skip.

Do you get a "check engine light" when you first turn the key on?

Check TPS voltage at idle. Should be less than 2.5 volts. (This is important.)

Check that injs are firing. Check both 1 & 2 should be yes.

Check for EGR valve stuck open.

Does the tach jump while attempting to start?

Disconnect 4 wire ign module connector. Turn key on. momentairly touch circuit 430 ( PPL&WHT). Scan tool should show some RPM. (It doesn't say how much.) If yes then you have a faulty connection or ign module If no then that curcuit is open or shorted to ground or faulty ECM.

Check that fuel pressure holds after pump runs for 2 secs with key on then off.

LMK what happens with these tests.

 

[berzerker]

Re: Will not start

my best guess on what's going on is a faulty coolant temp . sensor telling the ecm the wrong temp or you have a fuel pressure leak down issue inside the fuel tank . Got datamaster so you can see coolant temps before starting ?

 

[grimprime221]

Re: Will not start

finally got to use the injector harness tester and was not lighting up.

The temp sensor is new this spring. not getting any codes on regular scan going to try to figure out how to scan data just got that.

 

[Don W.]

Re: Will not start

Check TPS voltage at idle. Should be less than 2.5 volts. (This is important.s.

This is important because if the ECM sees more 2.5 volts it goes into flood mode and won't fire the injs. I suggest you check that just to rule it out if nothing else.