Inertia switch question
Thread Starter
|
New User
Joined: Apr 2015
Posts: 22
Likes: 0
From: Middle, TN
Inertia switch question
Greetings once again to the group!
I am having a weird intermittent problem. 88 302 EFI.
When I hit bumps, sometimes, the engine cuts out, not all bumps, seems like bumps that are more vertical oriented,,, can hit a hard bump, and not problem, hit the next bump, problem. Now I am suspecting the fuel pump is losing power. I am looking over the diagrams and trying to formulate a plan of how to attack this. I see that there is a inertia switch in the power supply feed to the high pressure fuel pump.
Is it "possible" that the inertia switch is opening momentarily when I hit a hard bump? Do these go bad in this fashion? Or is it that once they open they have to be replaced?
I am not discounting any wiring problem, but this inertia switch is something that I am not at all familiar with on how it is suppose to work and/or how it really works.
Thank you for your time and consideration!
billy
I am having a weird intermittent problem. 88 302 EFI.
When I hit bumps, sometimes, the engine cuts out, not all bumps, seems like bumps that are more vertical oriented,,, can hit a hard bump, and not problem, hit the next bump, problem. Now I am suspecting the fuel pump is losing power. I am looking over the diagrams and trying to formulate a plan of how to attack this. I see that there is a inertia switch in the power supply feed to the high pressure fuel pump.
Is it "possible" that the inertia switch is opening momentarily when I hit a hard bump? Do these go bad in this fashion? Or is it that once they open they have to be replaced?
I am not discounting any wiring problem, but this inertia switch is something that I am not at all familiar with on how it is suppose to work and/or how it really works.
Thank you for your time and consideration!
billy
Postmaster
Joined: Nov 2011
Posts: 3,533
Likes: 17
From: SW Florida
I have never seen one fail intermittent like that. They are either tripped open or not. If it does trip you can reset it by pressing the button on top, which is red on newer trucks and I believe white on older ones.
Not sure where it is on the older (pre 92) trucks but on the OBS trucks it's in the cab behind the trim panel by the passengers feet. It will be in the cab behind a panel somewhere on yours as well.
EDIT: just looked it up for you. 88 has it on the driver's side of the firewall inside the cab.
Not sure where it is on the older (pre 92) trucks but on the OBS trucks it's in the cab behind the trim panel by the passengers feet. It will be in the cab behind a panel somewhere on yours as well.
EDIT: just looked it up for you. 88 has it on the driver's side of the firewall inside the cab.
Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
When the truck dies, do you have fuel psi?
Best thing to do is hook up fuel psi tester and start driving. Then after hitting the right bump, pop the hood and see what your gauge says.
If anyone has experienced problems with the inertia switch, its been only a select few. And its just a rest switch. Once it's been tripped, it just needs to be depressed or popped back into the off(closed) position. I'm assuming that if its On(open) position, then its activated. Then it renders the fuel pump inoperative.
I don't know much more about it, maybe someone else can help everyone out.
As far as the cutting out, its either electrical or fuel related, and you just have to start at which one your losing. And you have already started a plan of action, you just need to narrow it down.
Best thing to do is hook up fuel psi tester and start driving. Then after hitting the right bump, pop the hood and see what your gauge says.
If anyone has experienced problems with the inertia switch, its been only a select few. And its just a rest switch. Once it's been tripped, it just needs to be depressed or popped back into the off(closed) position. I'm assuming that if its On(open) position, then its activated. Then it renders the fuel pump inoperative.
I don't know much more about it, maybe someone else can help everyone out.
As far as the cutting out, its either electrical or fuel related, and you just have to start at which one your losing. And you have already started a plan of action, you just need to narrow it down.
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
When this happens to an 88 most of the time it is bad wiring going into the sockets of the fuel pump relay OR the EEC power relay.
Most will then up grade to the newer stile relay.
The location of the Inertia switch:
1988 F-series fuel wiring:
/
Most will then up grade to the newer stile relay.
The location of the Inertia switch:
1988 F-series fuel wiring:
/
Thread Starter
|
New User
Joined: Apr 2015
Posts: 22
Likes: 0
From: Middle, TN
Thanks to all for the good info! 
I was assuming the inertia sw was a fault/reset thing, highly unlikely it would be a intermittent functioning device, but anything is possible.
Yea, going to go for looking at the power to the fuel pump, relays and such.
Timbersteel, I do not have a fuel pressure gauge, looking to get one, but the only time the engine cuts out very momentarily is when I hit a hard bump, so running it down the road and having the gauge out where I can see it , when it happens, seems to be a difficult task. I get where you are going with this, but I don't think I can make that happen. Good troubleshooting procedure though,
I was assuming the inertia sw was a fault/reset thing, highly unlikely it would be a intermittent functioning device, but anything is possible.
Yea, going to go for looking at the power to the fuel pump, relays and such.
Timbersteel, I do not have a fuel pressure gauge, looking to get one, but the only time the engine cuts out very momentarily is when I hit a hard bump, so running it down the road and having the gauge out where I can see it , when it happens, seems to be a difficult task. I get where you are going with this, but I don't think I can make that happen. Good troubleshooting procedure though,
Thread
Thread Starter
Forum
Replies
Last Post
MIKE861943
1987 - 1996 F150 & Larger F-Series Trucks
9
Sep 12, 2017 08:51 AM
