Is the ecu bad or would it be a relay?

What is your question?

91 f150 5.0, sat for 3 years and I need to get it started. After fixing the no spark issue, due to failed hall sensor. It still will not start. I have fuel to the rail, however with key on I can hear the ejectors popin on and the fuel pump running constantly, I’m leaning towards the ecu due to the ejectors, a pressure sensor wouldn’t cause them to pop on. I have continuity on all my grounds and powers, I don’t have a break out box so anyone know a good way to test this with out damaging the pins on the ecu

Visitor

·

Mar 20, 2019

·

2 Replies

Popular Answer
DaveJMon Mar 20, 2019

Yes, understood, a break out box is the way to pursue testing -- and there is no other practical way to test directly at the PCM. I do not feel like you have a PCM issue, mostly because unless there was some kind of trauma to it (electrical damage due to some kind of surge or water damage, for example), typically they do not need to be replaced. Are you saying you have fuel to the rail but not to the cylinders? Keep in mind you need fuel pressure and delivery, ignition spark with a properly timed engine, and the proper amount of air (cold engine -- basically choked of air). No vacuum leaks, no air intake leaks. You are saying you have a properly set distributor and the TFI (Thick Film Ignition) module is working properly -- spark is getting to the plugs? Certainly check for any issue with relays - there should be a PCM and a fuel pump relay in the box.

Reply
pushrodon Mar 20, 2019

Fuel pump not turning off .. I’d be inclined to suspect a relay problem.. Difficult to diagnose here online - as well as *hands-on* without proper schematic and diagnostic flow chart. God luck!

Reply
pushrodon Mar 20, 2019

Additionally - I don’t think you’re hearing the ‘injectors’ pulsing - can be confirmed using noid light.

Reply in Thread

Join the conversation!

Sign in or create an account to respond

Reply

Similar Questions

See more 1991 Ford F-150 Questions

What are the best Ford repair shops?

RepairPal Certified shops can diagnose and repair your 1991 Ford F-150. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
30 Certified Locations
Shop Image

Tuffy Tire & Auto Service Center - Grandview

4.7
(81)
2.39 mi
1524 W 5th Ave
Columbus, OH
Closed
Opens 8:00 AM Mon
Call
Shop Image

Excite Auto Repair & Towing

4.4
(15)
5.94 mi
3430 Westerville Road
Columbus, OH
Closed
Opens 9:00 AM Mon
Call
Shop Image

All In Auto Service

4.9
(22)
6.56 mi
5200 Fisher Road
Columbus, OH
Closed
Opens 8:00 AM Mon
Call
Shop Image

Tuffy Tire & Auto Service - Grove City

4.4
(520)
6.67 mi
2131 Stringtown Rd
Grove City, OH
Closed
Opens 7:30 AM Mon
Call
Shop Image

Blackstone Complete Auto Care

4.2
(35)
6.77 mi
4800 Sinclair Road
Columbus, OH
Closed
Opens 9:00 AM Mon
Call
Shop Image

Boyd's Tire & Service - Columbus

4.7
(178)
7.23 mi
5263 Godown Rd
Columbus, OH
Closed
Opens 8:00 AM Mon
Call
See All 30 Locations
30 Certified Locations
Shop Image

Tuffy Tire & Auto Service Center - Grandview

4.7
(81)
2.39 mi
1524 W 5th Ave
Columbus, OH
Closed
Opens 8:00 AM Mon
Call
Shop Image

Excite Auto Repair & Towing

4.4
(15)
5.94 mi
3430 Westerville Road
Columbus, OH
Closed
Opens 9:00 AM Mon
Call
Shop Image

All In Auto Service

4.9
(22)
6.56 mi
5200 Fisher Road
Columbus, OH
Closed
Opens 8:00 AM Mon
Call
See All 30 Locations