hard start-long time cranking

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i8av8

Donating Member
how can i tell if my walbro is hot wired?

when the truck sits over night it is very hard to start in the morning. i can prime the pump multiple times and still no start. can take up to 2-4 minutes of cranking and repriming before truck finally starts. then, it will start no problem once warmed up.

i put 12v to the grey wire on the firewall and pump turns on.
when truck does turn on i can disconnect fuel pump relay and truck stays running. as long as there is still fuel pressure i can restart the truck with relay disconnected. when fuel pressure drops to zero and relay is still disconnected truck will NOT restart.

pump is new but was sitting for 2+ years. did start truck every once in a while.
another thing is you can't even hear the pump prime up only a click under the hood. when i first installed the walbro (2 years ago) you could hear it very loud. now, nothing.
 
1blkc4

1blkc4

Donating Member
Re: hard start-long time cranking

I had the samething thinking it was the pump it turned out to be the coolant temp sensor unplug it before you start it mine started right up after I unplugged it .
 
It's just a six

It's just a six

Super Member
Re: hard start-long time cranking

Sounds like the pump is going bad? It's hard to hear the pump now, usually means it not pumping as much.

Put a temporary fuel pressure gauge to look @ your fuel pressure when starting.
 
randy merritt

randy merritt

Donating Member
Re: hard start-long time cranking

There was a post or question by me about this issue in the past, but I don't remember exactly, so please forgive me if I sound like I am rambling.

I was having the same issue some time ago, but mine was due to bad wiring by myself. The fuel pump relay will be "bypassed" by the oil pressure sensor if the relay is not working. I had a bad cold start issue after I installed my Holley HP because I had done the wiring wrong, and the fuel pump relay was not being triggered. After an extended period of cranking, the oil pressure will build up enough to "bypass" the fuel pump relay.

I suspect that you have a bad fuel pump relay.

Try hot wiring the pump with the lead by the dis. and see if the truck cranks right up. This would isolate the relay as the problem.

To qualify my advice, I am no great expert.
 
I

i8av8

Donating Member
Re: hard start-long time cranking

It's just a six said:
Sounds like the pump is going bad? It's hard to hear the pump now, usually means it not pumping as much.

Put a temporary fuel pressure gauge to look @ your fuel pressure when starting.
Click to expand...

2 years ago the pump was brand spanking new from one of the syty sites and it was loud when priming. now, you can't hear it prime up. just an audible click from the engine bay.

i have a liquid filled gauge on the fuel rail that fluctuates from 38-43ish at idle. prior to cranking it reads 44psi

olive top 50lb injectors. delphi i believe
 
I

i8av8

Donating Member
Re: hard start-long time cranking

i had a new coolant temp sensor for the intake sitting here so i put it on and same results. it did however, hesitate less after disconnecting the cts harness.
 
randy merritt

randy merritt

Donating Member
Re: hard start-long time cranking

CTS has nothing to do with this. Oil pressure sensor. If I am wrong, I apologize in advance.
 
I

i8av8

Donating Member
Re: hard start-long time cranking

randy merritt said:
There was a post or question by me about this issue in the past, but I don't remember exactly, so please forgive me if I sound like I am rambling.

I was having the same issue some time ago, but mine was due to bad wiring by myself. The fuel pump relay will be "bypassed" by the oil pressure sensor if the relay is not working. I had a bad cold start issue after I installed my Holley HP because I had done the wiring wrong, and the fuel pump relay was not being triggered. After an extended period of cranking, the oil pressure will build up enough to "bypass" the fuel pump relay.

I suspect that you have a bad fuel pump relay.

Try hot wiring the pump with the lead by the dis. and see if the truck cranks right up. This would isolate the relay as the problem.

To qualify my advice, I am no great expert.
Click to expand...

ramble on...
i appreciate ALL advice from any of yous.

i am guessing that i would have to disconnect the relay before the hot wire trick. is that correct? once the truck fires up it'll keep starting up so i will have to wait till it gets (engine) cold.

thank you all
 
randy merritt

randy merritt

Donating Member
Re: hard start-long time cranking

i8av8 said:
ramble on...
i appreciate ALL advice from any of yous.

i am guessing that i would have to disconnect the relay before the hot wire trick. is that correct? once the truck fires up it'll keep starting up so i will have to wait till it gets (engine) cold.

thank you all
Click to expand...
No, you do not have to disconnect the relay. It keeps starting because the oil pressure is easier to build with hot oil. Try swapping you A/C relay in place of the fuel pump relay. HTH.
 
I

i8av8

Donating Member
Re: hard start-long time cranking

randy merritt said:
No, you do not have to disconnect the relay. It keeps starting because the oil pressure is easier to build with hot oil. Try swapping you A/C relay in place of the fuel pump relay. HTH.
Click to expand...

no ac. i found an old fuel pump relay and it started up but i don't know for sure if that relay is any good. i won't know untill later tonight or perhaps the morning. ty has to sit a good while for it to act up.

if the oil switch will bypass a bad fuel pump relay what is the point of having that relay? is it just to prime the pump?

thank you very much for taking the time to answer my questions.
 
randy merritt

randy merritt

Donating Member
Re: hard start-long time cranking

i8av8 said:
no ac. i found an old fuel pump relay and it started up but i don't know for sure if that relay is any good. i won't know untill later tonight or perhaps the morning. ty has to sit a good while for it to act up.

if the oil switch will bypass a bad fuel pump relay what is the point of having that relay? is it just to prime the pump?

thank you very much for taking the time to answer my questions.
Click to expand...

The relay kicks in at start, then the oil pressure sensor allows current to run to the fuel pump once the engine is running.
 
Quickstop [UK]

Quickstop [UK]

Combating adversyty.
Re: hard start-long time cranking

If the FP relay failed with no bypass then it would just die there and then, wherever it was. It might be in traffic, at speed and with no PS or brakes, you would be in trouble. With this system, you are expected to arrive at a destination and kill the engine yourself at a time of convenience and be less likely to cause an emergency.
 
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i8av8

Donating Member
Re: hard start-long time cranking

thank you, merritt and quickstop for the explainations. i am just finding it difficult to diagnose.
 
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